It's too late to join now, but if you are around Des Moines, you can check on the site for their route, and put up prank direction signs, or some other funny stuff.
Next year join them, and get a tour of the Albaugh collection before the race.
http://www.roadrallycharities.com/events/midcoast/
Thanks to Bob C for inviting me to join, but I'm broke, and long way from Iowa