Absolutely. Someone must be legally responsible for the undertaking of the minors under their control, albeit someone who is running a business....as long as he (they) realize he's liable for their actions. So he should start exercising some guidance of some type, and start paying better attention to what's going on during his watch.
As for the fact they are minors, as long as there is a legal guardian taking responsibility there is little that can be done about enforcing the 18+ thing, especially if they have parental consent.
If certain players don't want to participate in events where minors are present, they shouldn't go (don't financially support some one who is running something you don't agree with)......set up your own events.
...as for trigger control.........good luck.