In reply to Cleanhands:
TR=TopRope.
Windcliff has easy access and the lower tier has plenty of easy stuff and is safe. Upper tier is generally harder and less sound and also only a couple of meters to drop off down to the lower tier (would be irresponsible to have a group of young kids up there I think).
Woodcroft Quarry is slightly less popular but has less in the way of kid-friendly routes.
If you're wanting to stay local then I'd say they're your best bets. Other than that you could travel a bit into the valleys to some of the South Wales sandstone quarries.
In the Wye there's not much that ticks your boxes. Ban-y-gor is steep and hard sport (might get a couple of things up Mushroom Wall but you'd exhaust that quickly), Wintours has some easy routes but they're all multi-pitch, and Shorncliff starts at VS.
I've not been to Black Cliff Quarry but that could be an option and would certainly be quieter than Windcliff Quarry.
Post edited at 12:39