My kids have slept over my moms house... and that's it.
They've spent most of the day at a couple different aunts houses... but they've only stayed overnight with Grammy.
There's certainly no rule that says your kids MUST sleep over someone elses house by X age?!?!
I don't think there's anything wrong with a sleepover
if the circumstances are right... even just for FUN, I see nothing wrong with them...
But I also don't see anything wrong with
not having sleepovers for your kids either.
It's all about what you & your kids are comfortable with.