It's important to remember that wound threshold does not have equate to hits and damage. Wounds can be a mathematical descriptor for plot armor. Children rarely die in these sorts of stories. A wound threshold equivalent to a normal PC could represent this.
Alternatively, you could grant the child 3 automatic unrecoverable critical injuries. This way, the PC is not spending most of their fights unconscious because a stray blaster bolt, but if they do suffer an unlucky hit, it would be pretty nasty.