I probably have the most amicable relationship with XH possible. I am still close with his siblings and their kids, so it's not unusual to run into each other. I'll exchange a few pleasantries with his SO if she is there.  How are the (her) kids, yada yada.

And no way would we all be going on a trip together!  That would be too weird for me.  Boundaries are your friend.

There's no right or wrong way; it's down to the people involved. If all of the adults are comfortable with taking a camping trip together then it's not a problem and it doesn't matter what anyone else thinks. But it's not reasonable to ask this of someone who would prefer that there is some distance and boundaries in the relationship between their SO and ex.

And don't whatever you do buy this "It's for the children!" nonsense. They do not need both parents/step parents on a camping trip in order to have fun. If you let it, you'll find over time that excuse will be used again and again to justify all manner of events and you'll end up feeling very resentful. It's much harder to erect boundaries at a later date than it is to start off with them clearly in place.

For the record, my response would have been a "Hell no!" the minute it came out of his mouth. But as BM here loathes both myself and DH (and the feeling mutual), it's not a scenario I'd ever find myself in.

I'm never quite clear why people divorce when they get along well enough to go camping together. If you are so concerned about happy family memories, and you like the person, why not stay together and work it out?

I think his situation is more uncommon tha n common and few people would be comfortable with it. I did stay in my sister's husband's ex's home for my step-niece's graduation, but that was a special occasion and it was very awkward for my sister. 
 

I wouldn't go, personally.  And if he really couldn't see my concerns, that would jeopardize our relationship. 

I only take hard stances in regards to boundaries when the relationship is toxic and unhealthy. I don't get my feathers ruffled by exes and SOs being friends because there is a HUGE difference between wanting someone in your life and wanting to BE WITH someone in your life. If there wasn't a difference, we'd all find it much easier to date bevause we'd just grab any friend and tie ourselves to them.

That said, I think you've nailed your own problem in this scenario. It's not about whether this behavior is right or wrong. It's about whether this behavior makes you incompatible. The fully blended family scenario is not for everyone, and if it isn't right for you, then this may not be the relationship for you.

My assumption would be that your SO believes he is compromising already to make you feel more comfortable, and there are likely silent compromises he has made without talking to you (like wanting to schedule a trip like this himself or declining dinner invitations from BM or whatever). If he feels like he's giving up everything he wants to appease you, and then you say no to this trip (which is totally ypur right), he may get very upset. He may feel like he is giving up everything meaningful to him, and eventually he won't give anymore.

Before you say "no" to this, ask yourself if you can compromise and go on this trip, knowing that he has been trying to change for you. If the answer is "no, I can't do it", then you and SO need to sit down and talk about your expectations of the future to see if you are on the same page at all. Use the trip as the flashlight that caused you to examine the hidden thoughts in your mind.

If, however, you can say "yes" to this trip, be honest (but kind) with your SO and tell him that you have reservations about this but you want to see how it goes before you judge too harshly and decide if you are uncomfortable. Then, plan on taking your own car out there so if it becomes too overwhelming, you can take a little escape (or leave if it gets too bad). Then, after the trip, have a follow-up conversation with SO about what you thought, if you would ever do it again, and if you would, how frequently.

It's hard to say whether going on this trip is a good or bad thing. I don't think that you know, either. If it were me, I'd go. It would give me the missing data I need. It would tell me if I could be comfortable in this kind of relationship, if my SO would recognize my uncomfortability and help ensure I am as comfortable as possible, and tell me if BM is genuine in wanting what is best for the kids or if she just wants my SO in her back pocket. BUT, I can only evaluate those things IF I go into the situation with an open mind that it might not suck. If you can't do that, definitely don't go.

This is a tough crossroads to be at because the numbers of ways it could end poorly is nearly equally to the ways it could end without incident. Either way, you're going to have to chat with your SO about your expectations and hesitations, and the difficult part is going to be crafting that conversation if you want to sustain the relationship. 

I never realized I didnt have boundaries with my ex. Steptalk has taught  me a lot. He was welcome at my house to hang with  the kids.  We did things together.  My boyfriend of 4 years didn't like it but went along with it but I never lived with that boyfriend. I realize now we were weird, enmeshed, whatever you want to call it. We broke up when the kids were 5 & 3. He moved in with his girlfriend shortly after. She was also invited everywhere by me but never came. I thought there there was something wrong with her... lol turns out I'm the weirdo!

When my kids were 20 & 18 they both were away at school together in an apartment. I was going to spend Thanksgiving with them. It was 4 hrs away.  I was going to ask their dad if he wanted to come but i didn't because I was afraid of what his live in girlfriend would think. He was down and out lost a good job then hurt himself at a temp job and then lost his car. I thought it would be nice for the kids to see both of us for Thanksgiving and since I would drive and we could stay at the apartment, it was a low cost trip for thr ex. I never asked and still regret it because 2 weeks before Thanksgiving he hung himself and I feel that Thanksgiving trip would have given him something to look forward to and changed the course of his life. We just "celebrated" the 5 yr anniversary of his death. I still talk to his girlfriend who found him dead and will never be the same.

So I went on a tangent and I'm not sure if I answered your question, but my point when I began is people are different but the girlfriend chose not to be a part of our enmeshed weirdness but her and I did become close for a while especiallyafter T's death (she was a good SM to my kids). It's really your choice if you're comfortable but don't let society dictate what you do. As my yoga teacher says...you do you.

For a start I hate camping.  I like my home comforts too much.   I do not have the sort of adversarial relationship with my ExH that DH has with NPD BM, we are friendly enough, but I would never want to go on holiday with him, it would just be too weird for words.  The nearest I have experienced to the scenario you propose is my brother and his ex wife who are pretty friendly, and although their children are all in their 40s, the two families (ie bro and his wife, ex-wife & her husband + 3 children and partners and the grandchildren) often spend Xmas Day together and have a meal.   But that's just one day and no nights.  A camping trip would presumably be a number of nights. 

I really don't think it's a good idea.  Tensions arise between best friends going on holiday together, so they are going to do so with your ex, aren't they?  And there is a need, is there not, to keep relations calm and friendly?  I just think it's tempting fate to put that kind of pressure there. 

For me, a lot of this entire situation would depend on whether SO and BM expected to be the leading roles in my own life. If everyone hangs out/ is friendly and that means that SO and BM are at the center of everything and stepdad and you are expected to be supporting roles, I'd nope out of that really quick. All of this is such a very small piece of my identity, I wouldn't want someone to try to make that everything about me. (Not sure if this is making sense.) I'm not a jealous person, and I wouldn't care about their friendship otherwise, so this would be my main deciding factor.

Tell him, sure, you'll think about it.  Take one second, say "hmmmmm" and then "nope.  Boundaries."

then walk away

Why would you want to hang with your SO ex.  Some one he had a sexual relationship with.  There had to be boundaries in a relationship.  One is the first relationship is ended.  If it's really ended there no camping trip. No spend thanksgiving, Christmas, birthday together.  Thay are not a family, 

you will be the third wheel. There. Big NO

when they divorce they ended the big happy family .  They don't get to play it out at other people expense 

I think your best point is your lack of free time. You have a limited amount of time away from work to go on trips - why would you want to spend that time with BM and her SO? It makes sense you would want to spend that time your friends and family or mutual friends - not with your DH's ex-wife!

I'd liken this to dating a coworker.  Things could work out, but if they don't and there's drama, it's really awkward and hard to escape. 

When you start to have friendly feelings for someone and there's a power imbalance in the relationship, you could feel pretty betrayed if they turn around and stab you in the back.  I mean, I was nice to Killjoy for years, which made her crappy behavior even more hard to digest.  Imagine if you start to consider BM your friend and she turns around and tries to get your income statements or something.  Best to keep your relationship strictly professional.  It's too much like hanging out socially with your boss.

Good fences make good neighbors.

Like u i have a decent relationship with hubby ex skids bio mum and yes every now and then we may all have to be in the same room for some reason xmas skids birthday or whatever may come up.  Usually I just smile go along with it. But going away together HELL NO. To me that just asking too much. I would start WW3 if he even suggested it. Ask him how many wives does he want. It good to gave a civil relationship with the ex. But then theres respect and boundaries. You have to ask yourself if the tables where turned would he agree to the same thing.