We do a benefit carshow every summer in Statesville. The biggest hassle is the judging (sorting vehicles into categories, judging, giving out awards). It takes a LOT of time and effort, and no one is ever satisfied with the results.
Its much easier to just do a cruise-in. Get some food vendors on site, invite all the local car and truck clubs, get some t-shirts printed and have fun. Might help to invite one of your local radio stations to do an on-site broadcast as well.
If you do give out awards, keep it simple. (Best classic, Best modern, Best Car, Best Truck, Best in Show). If you start getting specific with the categories, the judging will take forever, and you'll end up giving awards to half of the drivers who show up.
Send an email to the Carolina Regional Mustang Club at
http://www.ponytales.org/. They're based out of Charlotte and have a lot of members (and some sweet rides) in this area.