No, it's their home too, that's not reasonable.  Either talk DH into not having them, or go somewhere else for the weekend.

I think it's not particularly realistic.  It also does seem like you are looking for an excuse to not have them come over... period.. and not just because of getting sick.   

I mean.. masks all the time.. but at the dinner table.. covid magically isn't a "thing"??    Maybe if you feel that you should wear a mask.. or isolate yourself more during their visit it would help.  You could ask your husband to do his visitation outside the home.. only you know how that will go with him.  You can't demand it.. it's his home too and he is entitled to have his children over.. and barring them trying to actively kill you with the kitchen scissors.. kids bring germs in.. and while your son may not have theoretically given you the same experience.. your immune system could be much different now.. and it's not necessarily his kid's fault that is the case.  

You can insist your husband do all the care for his kids so you can avoid being around them closely.  You could ask him to limit them from certain areas in your home perhaps.  But, I don't think wearing masks 24/7 will be effective at all.  I don't think masks provide much protection period.. gaps in the sides.. poorly handled.. poorly stored.. worn improperly.. it is really not any kind of real protection.

It is not okay in any way. 

and then to have to go home and wear masks at home?  Nope.  You are asking too much

I'm wrestling with this same thing. We have Skids EOWE. I have no idea what they do or where they go when they are not with us. I also know that their stepfather and stepbrother work in retail and I believe that BM is not a big proponent of mask wearing. We'll have a new baby in our home soon and I'm anxious about them exposing her to COVID.

As much as this might be their "home" when they are here, the virus doesn't care and by all definitions they live "outside our household" for the most part. According to our state officials, spread in our region is now being driven by people gathering indoors with "close relatives" who live outside their household. Our state has also advised that anytime you are congregating inside with "people outside your household" you should wear masks. In addition, I've been told by my doctor that anyone around our baby - with the exception of myself and my DH - should wear a mask at all times. So, anyone saying it's unreasonable for SKids to wear masks in your home should consider the broader context. 

In my view, this is another area where stepparents are expected to give up control over something others would not dream of giving up control over...specifically, maintaining their own level of risk against disease exposure. I'm supposed to allow my SKids to come to my home with possible germs, because legally they are supposed to be at our home four days a month? I've avoided them so far during my pregnancy and will likely spend their time at our house isolating with my daughter. It seems a bit ridiculous that we will have to hide away in our own home, but I'm not willing to risk her health. DH is also high risk and would likely have serious complications if he contracted COVID, but I've had to put that out of my mind when Skids are around, because it's out of my control to ban them from visitation. 

And yes, DH and I have talked about not having them come over, but BM always threatens him with court if he does not take the kids and especially would now if it was due to our daughter. Even if she has no grounds, it would still lead to legal fees. So, this is a no win situation for me...and many other stepparents.  

I'm pretty sure you can't do that. Plus they have to eat and shower and sleep and all that. 

It's only reasonable if you're willing to do it, too. Not fair for you and DH to expose them while worrying about them exposing you.

Some practical tips would be to:

1.) Put hand sanitizer everywhere, including bathrooms. If they won't wash their hands properly, at least they can sanitize.

2.) Your DH sets up a cleaning schedule where he wipes down the bathroom, kitchen, door knobs, etc twice or more a day with an approved cleaning solution.

3.) Put Clorox wipes (or something similar) in the bathroom so everyone wipes down the sinks, toilet, etc after it is used (or at least so you can before and after you use everything).

4.) Get the best air filter your HVAC system can handle.

5.) Get an air purify. Might not help with COVID, but might help with other things.

6.) Open windows with at least 15 minutes once a day.

7.) Keep blinds open during sunny hours. UV rays can help kill some germs in your home.

8.) If you can get your hands on cans of Lysol aerosol, spray down common living areas once or twice a day.

9.) Sanitize your toothbrush (safely).

10.) Make sure you're getting recommended Vitamins C and D (don't overdo it, just recommended amounts).

11.) Do 15-30 minutes of cardio, preferably outside, to keep lungs in good function.

12.) Keep Kleenex easily accessible.

13.) Bleach/sanitize sheets and clean bedding weekly.

14.) Bleach/sanitize towels, and make them single use (don't use a bath towel more than once before cleaning).

15.) Wash reusable masks daily.

16.) Eat away from one another, and designate one person to cook and serve versus everyone helping themselves.

17.) Wash all dishes on the sanitize option.

18.) Get your flu shot, and stay updated on your vaccines.

There are likely dozens more tips, but this is a good start. If one of them gets COVID, visitation stops at whoever's house they're at. Same goes if they're exposed to COVID. 

Sure.  However, better to stop visitation until the crisis is over and go to Zoom visitation.  The beauty of being the NCP household is that the NCP can refuse visitation and the CP is on the hook to provide for and care for the kids regardless.

I would say if you are going to go with physical visitation and masks, then everyone in the home hoses down with sanitizer regularly and wears a mask.

Asking skids to wear masks, at times, makes sense to me. I am American but lived in Asia for a year in 2012, and it's all about how the mask-wearing is framed. If people see it as a punishment, then they will think it's cruel. But if they see it as the right thing to do to help themselves and others, then it is not cruel, just a part of life. For example, about three times when I was a teacher in Asia, a kid in my class came down with hand, foot, and mouth disease. That kid stayed home, but since the incubation period is 10 days for that sickness, we all wore masks for the next 10 days (except while eating and drinking), to stop the potential spread among my class, and we stopped going into the common areas (like the play area in the basement that many classes shared). It was boring and annoying, but a necessary precaution. I taught 3 and 4 year olds, and yes, they were expected to wear masks, and yes, they were able to do so fairly well. Asking your skids to wear masks while in certain common areas of the house is not beyond their abilities and is not cruel. Yes, it's somewhat extreme (by some people's standards and compared to what they're used to doing in their house), and they will need a lot of reminders, but it is a good lesson in caring about others and doing good deeds even when it's not easy.

Some people have stated that it is the skids' house too. Yes, true. It is the stepmom's house also. Why are the skid's desires of comfort more important than the stepmom's desire for health? Mask wearing protects them from each other as well--if one of them get COVID, the other may not get it. 

Unreasonable request.

If you're worried then you should be wearing a mask around skids and in the common areas. I choose to wear a mask in my home and distance when around my kids (luckily they are older and mostly self sufficient) because there was a case of covid at my work.  Unless they are symptomatic, the constant mask request for skids is unreasonable but hand washing every hour, deep cleaning with skids involved, taking vit C, healthy eating, are all reasonable.