It's nice that family's all get to go out cycling and learn how to be responsible on roads but there's no way i'd have a small child cycling behind me on a busy road like i often see. You really can't depend on car drivers seeing the child. Also if something's overtaking on the other side and a car has to pull in the child would be killed. Surely if they must cyvle on busy roads the child would be safer in front.
The other day we passed a man with two children, both cycling behind him and the smallest one (about 6) was wobbling precariously trying to keep up with dad, he could so easily have fallen into the path of a car, and the father wouldn't have even been aware, why put your children at risk.