Of course it's on a weekend when I have two other things going already.
I will look into getting the catalogs for you.
Treating it like the garden railway guys do is a good idea. If you do the kid interactive thing then you can cut a chunk out of the floorspace you need to cover.
For the theme - if you have limited brass track then I would plan on doing both. Have a mainline around the outside with a general modern setting, and then have a section set up like a theme park with it's own Western style train running in a smaller oval inside the other track. It could be a Western style theme park with an old town and a buffalo herd, cattle area. Or it could be multiple themes with a castle in the middle (can't imagine where I got that idea) and then lands from the different themes. You might even consider doing the entire thing as a theme park. If you do some custom signs and have a parking lot and entry, people will figure it out right away, and then you can use anything you want.