I would suggest not using the information here but instead going to your state gambling commission for info.
Here in NJ you must have a gambling license for all events that are 'tricky tray' style, have a 50/50 or a silent auction.
Even a kids event like picto (think picture bingo) is considered a form of gambling and has certain rules associated with it.
Hi! Because the auction is a form of gambling you need a license. Go to the town/city hall of where the event is being held. They will give you the paperwork to fill out. You need to get one from the town and one from the state (they will give you the state paperwork too). There is also a fee involved but it is nominal (we pay $10 to the town and $10 to the state here in NJ). If the event is being held in the town your school is in you can ask them to waive the towns fees. It can take a few weeks for the paperwork to be processed by them so get it done in advance. As for the carnival you will need to ask them. If you are holding it on school grounds and not town grounds that makes a difference and it is depends on what kinds of things your carnival will have, but the town/city clerk can answer all of your questions and give you whatever paperwork you need.
Definitely check on this. We have an auction at our Fall Festival and do not have to have a license or permit. I attended a gaming license training last year and nothing we do at our festival was included on their list.