Offer a first warning on any inappropriate behavior. Second warning would result in a punishment or suspension of some sort. Third would termination. Do not be afraid to suggest things for the mascot to do. Look at your entertainment tapes from the Blues Bros., Famous Chicken, Sport, etc. for ideas.
Mascots appeal to children first, women second, men third.
Today sports teams are trying to appeal to women and children more and more. Keep this in mind when you're marketing your mascot. Take a survey on women and children and see what they like about mascots. Do your best to always compensate your performer for their time. Chuck E Cheese is minimum wage.