Thanks for all the replies.
It has always been the case that we have stayed with the in-laws and they have stayed with us in our respective homes. We just used to have a much bigger home! I would have been much happier staying at a hotel and having a place to retreat when we visited them - particularly when fil was alive. But, that is their family culture. After being married 30 years now, that would be hard to change.
Dh’s sister is only 45 minutes away from mil. She brought up Thanksgiving to us only a couple of days after fil died. Thanksgiving is sil’s husband’s big family holiday to be together. She basically said, “You’ve got to take mil for Thanksgiving.” So we did - it was only three months after fil had died last year. I honestly was surprised that ds wanted to and was able to come for Thanksgiving last year and that he plans to come again this year. He is on the opposite coast, TG is such a crap time to travel, etc. However, he always has tons of airline miles from his job, and he does not have a SO at this point. Most of his friends are local and go spend time with their families. I am GLAD he wants to be here for TG! But, mil is definitely coming then - and probably again at another time - she’s already mentioned coming in February for her birthday.
I don’t really think ds minds being “trumped” by his grandmother. I am the one who minds. And, I kinda mind that dh doesn’t see why this bothers me. Ds probably DOES appreciate having somewhere else to retreat. There really and truly is not room for an air mattress in our condo. Our coffee table is heavy with a glass top - not easy to move. I can’t stand the idea of his sleeping on an air mattress in the kitchen. That just seems icky. Plus, I want ds to WANT to come, so I want him to be comfortable. Honestly, he gets the better end of the deal because we only have a sleeper sofa in our second bedroom (thought it’s not as bad as it sounds - it is some fancy kind - does not have a bar in it and is reported to be quite comfortable), and ds will get a “real” bed whether he stays at our friends’ place or we rent something for him.
Maybe what is bugging me is that it apparently hasn’t crossed mil’s mind that we might prefer ds to be here with us instead of her. She had “booked” with us first last year before we knew if ds could/would come. He wound up working remotely two of the days he was here (so that also made it nice that he could retreat to our friends’ place). I feel like we are going to be “stuck” with this situation as long is mil can travel. That sounds pretty mean, doesn’t it? We do hope to buy a larger condo eventually, but that is probably four Thanksgivings away.
I’m not sure of the answer on how to define “immediate family.” My parents both died before dh and I married, and I have no siblings. I think if I am being honest that at my core I struggle with our always having had to spend holidays with dh’s family and always having to “share” ds after he came along. Pretty selfish, eh? And, whether rightly or wrongly, I think daughters typically stay closer to their family of origin than do sons. That is a BROAD generalization, I know.