I agree with what the others have written. Combining the event with another club would increase numbers and add to the variety.
I really like the cruise idea. Must admit I was thinking about this during the Nationals. My son really wanted to go in the Cobra with me and we would have driven it to the dinners (when the weather was cooperating) but the track gates closed at 6pm so I wouldn't have been able to garage the car for the night. Also, being under 16, he was not allowed on the track which was a bit of a bummer. He'll have to wait until the 30th Nationals for his chance!
Are the Nationals promoted in the Golbourn area? Do the residents know much about it? If it were, that would bring more foot traffic during the event.
A large screen TV in the pits with live streaming of the drivers would be great. Would help to involve the spectators. I noticed that someone had a drone. Footage from above of the cars competing would be great to see.
Re the vendors, let them come for free if they want. There is room for them, and that would add to the weekend. Maybe they can have a carnival area for kids with jumping castle/ball pit etc. Those artists who do cariactures would also be great to have. Perhaps a portrait of owner with car could be a door prize?
All in all however, my son and I had a great time. Even if nothing changed, we'd still be happy with that.