Hi V.!
What are your son's sleep habits? Does he stay in his own bed? Does he have a hard time going to sleep? Is he afraid of the dark? Has he ever spent the night without you?
My son has had "sleep overs" and he's 5, but they have been with his cousins at his Auntie's house.
I think sleep overs are a great way to encourage their independance from us. But you still have to know they will be safe. I wouldn't let my child spend the night anywhere unless I knew the family and felt comfortable.
Good luck and hope this helps!