In reply to ashaw:
Fairbrook can be quite fun.
Seen a few kids groups using it, fully kitted out in caving style overalls, helmets and buoyancy aids. We used to just scramble up as close to the water as possible. A few slightly tricky small waterfalls, but everything is easily escapable.
Its not what I'd call a true gorge though! But you can make it more fun by sticking strictly within the "banks" of the stream or something.