Children shouldn't use hand signals, because signaling may cause them to lose control of their bikes. They are an important communication link between cyclists and motorists. Any child who does not have the skills necessary to use hand signals without falling or swerving shouldn't be riding in the street to begin with. Many accidents involving older children occur when they fail to signal motorists as to their intended actions. Bike reflectors and a reflective vest will make it safe for my child to ride at night.
Night riding requires special skills and special equipment.
Few youngsters are equipped with either. Never allow your child to ride at dusk or after dark. I don't need to teach my child all of this bicycle safety stuff. I was never injured as a child. Biking is just meant to be fun.