i would let everyone know that 3 emails ( or pm's) will be going out to participants, and a reply will be needed on all 3 before you will be officially entered into the contest...send them out a few days apart.( good luck writing the software for this)

or

just make it part of the contest like it always is, and its the luck of the draw.

or

make it real interesting, almost like a family reunion type deal, where ya pick your own team, and come back every year and try and beat the last years team.... with a trophy that passes from state to state and needs to be relinquished to the next years winner.