I agree with DNA. Your question did make me wonder about the existence of an online race management software, and I found this: http://racemanager.sourceforge.net/ Not online, but open source (read: free). No idea if it works or anything else, but it could streamline things for you.
Also, is your race exclusive to the boys in the Pack? You can generate a lot of excitement and turn it into a bigger event by opening it up to Dads (and Moms) and siblings. It lets me be more willing to let my son do things to his car that leave it less pretty, or perhaps even slower (but doing *his* best), while still doing my best to make the fastest car I can (going for first place for the 3rd year in a row).
This year, our Pack is advertising the PWD at our church (who sponsors our Pack) to bring in boys not yet involved in the scouts. We're bringing in some cars from previous years for those boys to race with in their own races.
- Eric