You should contact local recreation vehicle places.
Powers Motor Sports is somewhat near Allendale. You could call some marinas, etc.
I go to GVSU, and live in Spring Lake. I drive by the pits almost every day.
I just picked up a 87 JS550 right near the new light in Eastmanville. I should have it ready to go by then, if not, I will just jump on my 95 750SX.
Sounds like a pretty good time though.
I think with the right promotions, you could make it quite a spectator event. Sure you can get riders, but to have spectators that would be icing on the cake.
KLQ is a great start. WGRD sponsored a car show at GVSU, so maybe you should contact them. They have a sweet van that has a sound system that can play to an audience of 300. They seem to be much more willing to support the community.
I would also try and get WZZM to back you up.
Just a couple thoughts.
-Josh