Get your directors involved by seeing how much money the crowd would give to get them to dive in, too. Many schools run a festival or band day for high school students. Money comes from registration of the high school members, t-shirts, or help from the college program. Ask your music department first if they will be willing to help with the festival because it is a great way to recruit future band members. Your chapter can organize and charge money for tickets to such an event for your band program.
Themes are always a good idea.