I've just given this a plug in the What's On section but I thought lots of people would be interested in hearing about the sessions for children and teens that Flying Fantastic offer.
I've been to the sessions for adults using the aerial silks but they do separate sessions for children. They have silks, trapeze and hoops and I imagine children would find it great fun.
If you are an adult reading this thinking you would like to try it - I would thoroughly recommend it. I'm a total beginner and found it very enjoyable - but extremely challenging too (in a good way). Great for upper body fitness and strength.