I made a rule in our house that we don't do sleepovers. But I felt it had to go both ways. If I allowed someone's child to sleep here then I felt they would be offended that I wouldn't let my child sleep at theirs. So it was a no sleepovers both ways rule. For our immediate family it's different. The children have slept at both grandparents houses and my eldest has slept at his cousins a couple of times.
Now they are getting older I have to reassess. My big kids are 11, 8 and 6. I still won't let me boys sleep over as I don't feel comfortable with the parenting styles of their friends. But this week my daughter slept at a friends house and is going to a slumber party this week which she has said she does want to sleep at. (I give the choice to be collected at a late hour and let the other mum know I will collect if need be at any hour if she changes her mind) Also I only let her sleep at a house where there is no boys. Basically it depends on the family and my relationship with the mother as I am basically entrusting my child into their care. Btw my daughter is almost 9.