Hm. Black Hill slabs may not further endear climbing to them!
Frogs Hollow and Deceit will probably be the best for them in that area, with a tight TR they will hopefully be able to get up them.
If you're not too wedded to Black Hill then Dog Rocks at Mt Alexander is also a pretty good kid crag (sorry, this may not be news to you)?
Hope you all have a good day,
Ben |