Excellent!! You will be excited. Now you don’t need to be scared to death that any shoes will drop.
If the school has vending machines…ask the organizers if it would be ok if you sold soda and/or snacks. Some vending machine contracts (especially to schools) have language in them that can go beyond any “sure go ahead I don’t see why not” if not checked to “who told you… you can do this?” Never assume it is a given….outside or not if there are vending machines.