Kevin has earned himself a thorough chewing out in front of his cousins, so they know this is a really bad idea. I'm going to include the fact that if something had happened, even if it wasn't his fault, we'd be SOL, because the insurance wouldn't cover him.
At this point, his cousins will be sent to their father's to explain their part in this (I hate 'daring' to do stupid stuff like this, but I don't consider it a spanking offense). I'm pretty upset with Kevin, but I think I need to calm down and think a bit before I make a decision. I hate that he did this at a party, but I'm going to tell him to go on. He's old enough that we can come back to this later, and he'll still know what and why.
I'm pretty sure he'll be getting worn out tonight. This was irresponsible and immature. Since he doesn't have a license, there's nothing equivalent I can take away, so a sore butt should be immature enough punishment to match his behavior.