I think sleepovers are a great way to teach your children independence. When I was little I was very, very attatchment to my parents. I didn’t like playdates or babysitters ( I was completely normal bH just a “mamas girl”. My first 3 sleepovers atleast, my dad had to come get me before midnight, but over time I got more comfortable sleeping out and it helped me to not be SO attached to my parents. I don’t think you should send your child on a sleepover kicking and creaming c’v but it’s ok for them to be a little home sick once in a while.
And it should go without saying make sure the house has acceptable kashrus etc.