I think nearly all familys have a holiday in cornwall or Devon, well the ones who live closer to the S.East of England are more likely too have done. There is a place called Chedder Gorge, in or near summerset, and it is amazing! All the rock formations are made over thousands of years by water and limestone, some of it has been dug out and been pathed so people can see more, But it is an amazing sight. You are taken through by a guide, he also talks to you and tells you different parts of the caves history. He also points out limestone formations, when I went last year, they pointed out a lump of limestone on the floor, it did not look like much, but then he pointed out that it looked like an elephant! and It did! there was a couple of things like that. There is also a paper mill there and you can have a go, but it is a bit messy! but fun.
I loved it there, but I personaly would not take very young children in there, as it is quite dark, and some parts of the caves are very slippy, you would not be able to take a buggy through the caves as there are a lot of steps to go up at some points, but even so, It is a great place to go.

The price to get in varys depending on the time of year, but at a rough guide, I paid about £5.00 per adult, I had no children at the time, so I can't comment on prices for them. they also close the caves for some of the year, so look up their phone no before you go and cheak they are open to visitors when you want to go.