First car show -- advice??

Collectable sounds right, double check with the organizers.
Formal car show, or casual "cruise-in" style?
If formal, load up all your cleaning/detailing supplies and be prepared to spend time prettying it up when you get there.
If casual, wash it down and dry it before you leave, throw some lawn chairs and beer cozies in the trunk, wear comfortable shoes and try to get a spot in the shade!
Either way, have fun!