Ideas for a "Bike to School Day"

I'm a high school teacher, and I am thinking of organizing a bike to school day. I'll get the school administration to sign off on it and publicize the event with posters and announcements. What kind of event? What else could I do? It would be cool to have some kind of event and maybe a raffle for people who come to school on bike. Any other ideas? I thought I'd contact the local bike advocacy group and see if they had any suggestions. I can probably scrape up some money (maybe a couple hundred dollars).