This topic has been done to death, but as the Summer holidays are here when families hit sunny European destinations, please remember many hire shops give out equipment to just about anybody and sometimes poor advice, the equipment is not safe for little bodies, most VF are designed for adults, children can be unpredictable particularly when frightened and any parent would be devastated if their child was hurt as a result of misunderstanding VFs as a glorified ropes course.
I bailed out a parent doing a high mountain lift accessed " Facile" VF today with an over confident 12 year old competition climber and her two terrified/crying brothers of 6 and 8. All were trying their first VF, which was recommended to them by the hire shop next to the cable cabins in Serre Chevalier.