You could see if some PFs in the US are willing to let you borrow some brass track and send it back after the exhibition. Seems western would be really cool, and honestly, there being the limiting factor of there only being so much you can do with western theme might help you bring ideas into focus. There's so many possibilities with a modern theme, it can be hard to form a plan in so little time.
Keep in mind that if you use green felt, klickies won't stand quite as well on it.
Getting the kids involved would be really nice. You could do a cowboy version of waldo.

Also, guess how many type games, like guessing how many bicycles, puppies, cats, whatever in the jar would be a good game to give a way a prize. And you can do something like spotting the things that don't belong, like a motorcycle at the hitching posts, a TV in the sheriff's office, that type of thing.