A.C.
We just did this with our son who turned 8 last December... our theme was a "Wii sleepover" and we had 7 boys there. Here's my advice:
1. State the rules right away. For example, no one goes upstairs or in the basement, ASK if you need something to eat/drink that isn't on the buffet, no throwing balls inside, etc.
2. Be sure to have plenty of snacks and drinks out so they can serve themselves.
3. Have plenty of things to keep them interested and engaged in the party.
One thing I noticed with the Wii is that only 4 could play at a time, which left 3 out on each game. So, we struggled with making sure the boys took turns nicely. For those who weren't playing Wii, we had the computer set up with games, and we also played board/card games with them. Movies are good, because they are ALL involved. So, bottom line, if you have enough activities to keep all of them involved and engaged they won't be wandering around your house!
People thought we were nuts to have a sleepover with so many young boys, but it went really well... the kids still talk about it to this day!
Have fun!