First, find out what HE thinks a sleepover is. what has he heard. Know his expectations and weigh them in.
Either way, you can set some natural ground rules that make sense as there is a variety.
Some kids expect that it is a stay up and put ice down the back of someone who falls asleep. Not a great idea. At this age, I'd make a bedtime rule.
Review your house thoroughly for any guns, weapons, alcohol, medications, car keys, that need to be locked up and out of sight. There are always adventurous kids that will experiment even though they know better.
Limit it in size to make it manageable and tell your son that he is second in charge to make sure things go safely and happily so that you can see before you grand bigger ones in the future.
Figure a way that they absolutely cannot leave the house through a door or window to explore, teepee a house, vandalize, whatever in the middle of the night. Don't be naive.
On the food side, watch out for too much sugar as some kids get super hyper and that's bad for your house and the other kids.
Have some interesting things to try: board games, appropriate movies, etc. Talk to each mom to assure them of what steps you've taken to keep them safe and sane.
Don't ignore and wish for the best. Check in on them to make sure all is well but use excuses now and then like brining in a snack or asking a question or something. Let them know they can't depend on your ignoring them. And yes, that means in the middle of the night too. Set your alarm.
You set the time they come in and the time they leave and ask the parents if that works for them.