I think children can defend themselves...no, I don't think they could drop someone with one shot, but they could make enough of a scene that the attacker might think 'Screw this, I'm going to attract attention in a minute' and give up. A friend of my mother's told us how she had been trying to get her autistic child into the bath (oh, don't you all just love me and my surreal anecdotes?). The child was refusing point-blank to take her clothes off, so this woman relented and said she could have a bath with her clothes on. She picked up the girl to put her in the bath, the latter kicked out wildly and managed to hit her right in the solar plexus, severely winding her. (She was on the phone to my mum and apparently she was still having difficulty breathing.) Now translate that to a real life situation, I reckon that would have given the child the chance to yank away and run for it.
