Just a thought, you might wanna give the cops a heads-up. You could let them know what's going on, just in case, so you don't have to go into a huge explanation if things deteriorate.
I HOPE that wouldn't be necessary at your daughter's party. Might make it more "memorable" than you want. Hey, with any luck, his family will be so insulted they will boycott it!
Probably just a dream...