Things to do with older kids in Bath?

[belledejour]

No, not IN the bath...in BATH!
We might have a night there over Christmas/NY en route for West Country. Is there any fun stuff for older kids aged 12, 10 and 9? Of course there are the Roman baths, but what else might appeal?

I know it's not Bath but @Bristol is fantastic and only about 15 mins from Bath on the train.

The Jane Austen Centre
Fashion Museum

The Assembly rooms (free entry) and 1 Royal Crescent. you can get joint ticket for the Roman Baths and the fashion museum which saves quite a bit and was worth doing because I don't think the fashion museum is worth the stand alone price.