Build the arena
Advertise competition day - newspapers, flyers, banner for tech lobby. Flyering.
Get MC/robocasters
Music compilation
Get seating, including upstairs
Print giant checks and award certificates, certificates of participation
Set up sound system, including upstairs
Set up video and projector
Make brochures for visitors, including rules & teams. Also nametags
Make the bracketing system, including team placards near the arena
Get food for competition day - breakfast for the teams, lunch for everyone
Tee-shirts for team members
Clean up