Fun activity for 11 & 9 yr old somewhere between Stoke-on-Trent and Northampton?

[JustAnotherManicUsername]

What would be a fun way of spending a probably cold Sunday in November, somewhere between Stoke-on-Trent (where we're visiting Water World on the Saturday) and Northampton (where we live). Could do a detour of an hour or so. Best bet so far seems to be Chatsworth gardens + playground because it's supposed to have a really good playground and my kids like gardens (house is a bit expensive). But they're not going to love it like I expect them to love Water World so I'm wondering if there's something more exciting we could do instead. Not sure what kind of thing that would be though!

Nerf Zone in Matlock. Suitable for ages 6 and above, children get armed with their very own target vest, goggles and a nerf gun. There's a training zone where children can prepare before entering the arena.
Speedwell Cavern at Castleton. A boat tour through network of cave 200 steps underground.

Snowdome in Tamworth?

Thanks. Caves look good although a bit of a detour. Nerf and Snowdome we can do locally so fancy something different. I found some nearer caves but they seem to be closed for winter.