Hi Digz,
I might be the first to reply, so welcome to VE forum.
I'd be tempted to go for a route in the Little Berg first as its warmer, more fun in the rivers and still has grandeur. I'd also be tempted to stay in a cave rather than a tent because caves give you so much of a homely feel in which you can spread out and be comfortable. If it rains, a cave is just great whereas a tent is a bit more of a lie-down and pass the hours kind of thing.
I'd consider Marble Baths, Xeni, Lower Injisuthi or one of the caves in the Monk's Cowl area. I'd stay away from the top of the Amphitheatre first time round because of the theft issue. Its unlikely to happen, but if it did, it would be a real downer for the children on their first trip.