Am I overreacting?

My in-laws have offered us to stay there while trying to catch up on some things. Well I had an idea and it got shut down like immediately. There are 2 rooms, 1 room which will not be changing much like bedwise, etc. So we talked it over today and I was like, I want my child to have his own room and that I could sleep in the other room(that’s set up with a tv and bed.) Then she goes on about how her other 2 grandkids should feel comfortable enough to come over and play. And I was like yes, of course, they would. She’s like I know how you are about your child’s things and I was like meaning putting them up because they are pricey? And she’s like yeah, I want them to be able to share. I was like they will what I put out in his room, the rest will be put up for sure because well I pay for it and I want it to stay nice and that way my child can enjoy them for a long time. So like am I crazy or what…for thinking that my child should have things that are valuable to him and we don’t want other kids destroying them? So basically she wants like no rules and are allowed to touch whatever they please. *I buy literally 99% of his things. Told me that my child will learn to be selfish when all I do is watch other kids full time and he shares the toys that are in his room and everything else that I don’t want touched is put up in his closet.