[Symbiote]

I have done this as a child with my grandparents, but I'm not sure there's that much difference from an old/worn (less smooth) commuter train at a similar speed.

For a child, I think a better experience is visiting a larger preserved railway. I liked visiting the locomotive works at Loughborough (Great Central) since age 8 or so I was shorter than the largest wheels of most locomotives. I'm not sure if it's still the case, but back then we could walk close enough to risk getting grease on our clothes. From Google review photos it looks like it.

(From the article, I'm still shorter! They're over 2m in diameter.)