I think you can still coparent successfully without doing things together. There is no need for "family" barbecues, prolonged conversations at visitation exchanges, etc. Obviously, you will be around each other for skid events - school functions, sporting events, etc. but even there you can sit apart and keep pleasantries to a minimum. You can still be civil and coparent without being friends and feeling the need to spend time together. 

My DD is only 10 months old but she has only spent a few minutes total with BM in her whole life. Quick exchanges, minimal contact outside of exchanges, etc. DH has two brothers who were kids of divorce and DH barely recalls seeing their Dad during their childhood. DH knew his brothers went to their Dad's but he never really saw their Dad except for if he came to pick them up and even then, DH said he waited outside or in his car. 

That seems weird to me. Don't they have any friends or something? 

I'd worry that being best buds with bm would really confuse the skids and give them entirely the wrong impression of what a marriage is. By all means, be gracious and cordial when you have to be around them but there is no reason whatsoever for you to have them in your inner circle. Start cutting the drop-off conversations short to discourage their imposition in your life. 

BM's contact with my DD3 is minimal. We do not do activities together - I made DH put a stop to that before DD was born because *I* didn't like it. DD always wants to say hi to BM when the SDs are Facetiming with her, and she might see her on the rare occasions when we have dropoffs/pickups that aren't at the school bus stop, but I'm ok with that. BM is a decent person, so while I don't want much to do with her, I don't worry about DD having some contact with her. 

No joint party's, No BBQ,  no need that person and her family in your life.  You will have to do Graduations, wedding, with her but that will be many years away.  Some people do it, I just don't understand how 

My BK's have never met BM. She showed up unannounced at our house a couple of times but fortunately my BK's weren't home. After telling her outright not to come to our home ... and glaring at her she finally got the hint that she wasn't welcome on our property.

One time, being the weirdo she is, BM started following me and my youngest BK at the grocery store. I finally blocked her with my cart and stared at her until she backed off and left. I didn't tell my BK who she was and since my child had never seen her before they didn't notice or realize she was stalking us.
BM is a dunce, she has no pride or self respect and she is intrusive as hell. No idea how someone so dumb has such big balls no matter how stupid they make themselves look. 
My DH is 100% on board with not hanging with BM so that helps. The only person who has suggested we all hang out together is a female relative that has never been a SM but thinks she is a therapist that will fix all our family problems even tho she came from nutzer parents that she has no relationship with. Her biggest accomplishment was to marry well so she really doesn't understand anything about step families. 

presenting the failed family as anything but what it is does not help anyone IMHO. Particularly the kids.  This co-family bbq, extended banter at hand offs, etc... reeks of something being off to me.

Civil, absolutely. Glad-handy.... nope.

We had nearly zero F2F interface with the SpermClan other than in court,  with the exception of maybe 3 direct hand offs for visitation over 16+ years.

The majority of the telephone interface was contentious with SpermGrandHag ranting, etc.....  

None of us would waste the hydration to piss on the Hag if she were on fire.  The rest of them....

meh

If we did have 'ours' kids, I would not see much difference. We stay the hell away from nearly any risk of face time with the blended family opposition. We did this for the health and wellbeing of our kid (my SS) and the health and wellbeing of our family.

SS's visitation time with them was his time. We made it a point to not interfere.   Neither did we tolerate interferance from them in our family time.

When me and DH first started dating (when me and DH tried being cordial with BM) BM offered to have my dds spend the night at her house, or she'd watch my kids while DH and i went out... i barely knew her... and my mom always liked watching them, even if i wasn't going anywhere, my mom liked them spending the night once a week, why would i let a complete stranger watch my children if my mother ENJOYED watching them? I want against them having play dates, but i wouldn't leave them with people i didn't know. 

Which I'm glad i never did, BM ended up being a psychopathic narcissist, and SD was manipulative and mean, my kids would probably end up "in trouble" at BM's house.  So, yea, BM has VERY little to do with MY kids. 

I would keep it separate especially considering the distance.

I have a wonderful stepdaughter and when I visited her with my five other children she wanted to take those five to an event on her dad's side. I was stunned she even asked but I know she was ignorant. I explained to her that I expect her to be an adult and that she needs to understand that I do not like her father's side for the many things that have been done to my wife and me. She was frustrated, but I stood my ground and she had to understand that my children do not belong to her dad and I do not want his influence anywhere near them. 

As she has gotten a couple of years older she has gained more perspective.

I could give a list of other interactions where I tried to work with bio parents after adoption and it was a complete disaster because they become entitled and thought they have rights they don't have.

I have learned to keep a strict distance between the parties. My family is my responsibility and I don't want to add drama to the situation.

If I dealt with a rational other side then I could see myself making an effort, but that is not my situation.