So you're trying to model either 15" gauge live steam or 7'-1/4" gauge [1:8] live steam? Looks like you're going for 15"!! look to the wikipedia page for more info...it's vague, but I think it's good enough. There's mention there of 1:2 and 1:4 scale operations being done. Live steam - Wikipedia, the free encyclopedia
I had thought about doing something similiar i was going to do it in a city park or around a downtown block so the scale could be a little more flexible. We have several small towns that have kiddie rail roads that are mocked up out of probably lawnmower parts, but it is fun for the kids. Couple Z flat cars with HO kids pointing and laughing and I think it would look nice. Since I'm not doing exact park replica of a ride...I think it should be nice.
I would say flats. or gondolas. check the web sights of dillerent live steam train clubs to. :thumbs_up: