Conspiracy, assault(aggravated), assault with deadly weapon, etc etc.
First the kid is stupid for challenging 5 guys with weapons.
Second, you WERE 5 GUYS WITH FUCKING WEAPONS. This kid challenges you, do you really need to do anything? You know you're gonna fuck him up if you go after him. He's probably shitting his pants no matter what he says.
Is your girlfriend not grown up enough to be able to handle this shit on her own? I mean what are you guys gonna do when she orders a happy meal and doesn't get the prize?