OK. It's not "technically" a children's activity, but I think they'd like it best. Puffing Billy is a historic steam train, lovingly restored. The folks working it are almost all volunteers, and they dress in period costume.
It's "traditional" to ride sitting in the windows with your feet sticking out. People along the short route come out to wave as the train passes by. I'm not speaking of only the people who happen to be stopped by the train as it crosses the roadway. I mean there are folks who set out chairs and wait for it so they can wave as the train passes by. It's a short, scenic ride and lots of fun.