What a great idea! The Sig Eps while I was a collegiate not that long ago did the "Kindergarten Olympics" as their event and all the sororities loved it because you didn't have to be the most athletic to compete. One of the events was a tricycle race....good times good times!
It sounds like you have a great idea brewing that could earn some money for your local or international philanthropy and bring the greeks together. I would even recommend inviting the MCGLOs and the NPHC orgs as well, make it a truly greek event!