I had a similar dilemma. Mil went in for years about dc sleeping over, kept showing them the spare room and saying this is where you’ll sleep when you stay with granny.
i wasn’t comfortable. So I said no. When dc got older they expressed that they did not want to stay. It was annoying, but we had no “need” for the childcare so never found a reason for them to stay.
made worse I think by the fact the older grandchildren stayed a lot as their parents wanted the overnight care and used in laws as free childcare constantly. So I think they thought it was us being awkward. But ours are much younger so il’s were older, plus I saw the dynamic with the older grandchildren and preferred paid childcare. Heavy smoking, left to their own devices or the younger being left in the care of the older ones, boys being allowed to play video games and do what they wanted while the girls had to help with chores, that sort of stuff.
interestingly my parents never ever asked or pushed, and I was happier leaving dc in their care.
dc are adults now and stay fine away from us. One was always fine about sleepovers and has moved out into shared accommodation. The other doesn’t like sleeping away from home unless holiday etc (bit like me) but is saving up so they can afford a studio flat.
again an interesting observation is out of the 5 older grandchildren (all now 30- 35) that stayed at il’s a lot, one still lives at home, the others all lived at home until their late 20’s/ 30’s when they moved in with partners/wives/husbands. None ever lived independently in their own or shared houses, or moved away for uni etc. so I wouldn’t say staying away from home leads to independence.