Hopefully you can create two flexi class's. One that is fairly open for the more experienced racers--and a simple LMP class with SEALED motors etc for the rookies. Perhaps you can have a rule that once you've won 3 races as a rookie you move up to the other class. That may encourage more newbies to give it a try.
Advertising the track anywhere in the area? Local hot rod shops-- etc?
Good luck with it!!