If you charge for kids to stay at your school for a Parents Night Out event, you may be in violation of your state code. The issue is that you are charging to take care of the children. That makes you a daycare center (even though it’s at night, the law still applies).
The way to stay safe is to make the event free but charge for food and drink. Give the kids a wristband that shows they paid. Jim King in Orlando did this last Friday for $30 per child. He grossed $2,200 and enrolled a summer camp student from the guest list.