Boot me out if you think I'm butting in, but some observations across the pond which may or may not be valid.
From what we have learnt in the UK (granted we are about as big as your states but I think these observations will be more valid in your case).
the first Nat meet we held was for one day in a field central to most. It was a basic show and tell with a hastily arranged competition. best dash, best boot, most ghetto, best overall, and most original idea. Prizes were donated by UK suppliers we got to come down.
the last one (4th meet) was over a whole weekend with some people staying the whole weekend, others just coming for the one day. again the same competitions, but also some fun things like go carts, minor off road rally, xBoxs/playstation on big screens. etc.
Oh and barbecues as well for food.
so my recommendations
1. try and make it as central as possible
2. make it a Friday night to Sunday afternoon thing (gives more people the chance to turn up at least one of the days)
3. Try to get suppliers involved, they can set up a little stall and maybe sell some products at a small discount (and of course no delivery charges
). They may want to supply prizes for comps like ours do.
4. Have other things to do IE that kids will be able to do then people with kids will be able to bring their kids and be happy they won't be bored. (that again will allow more people to attend).
As I said just a few suggestions from across the pond.