If you're concerned with the moral implications of how it translates to the real world, then superheroes are a wrong idea. I would never support vigilantes running around employing violence in the streets, in real life. I love the Punisher as a fictional character, but anyone trying to do that in real life would be the exact opposite of a hero.

Kid superheroes are okay because, in the fiction of superheroes, the underlying narrative is essentially that the heroes/good will triumph over the villains/evil. This is also why violence in superhero stories gets a pass as far as morality goes -- in a superhero story, any violence on the part of the good guys is always ultimately to the greater good -- unlike real life violence, which is nowhere near as clean-cut.

Put another way, superhero stories are not meant to encourage the audience to literally put on a costume and go engage in some vigilante violence. We are meant to understand that part is just action/entertainment. The moral message is meant to be encouragement to act with virtue -- that, if you act with virtue, you will make the world a better place. Given this, yeah, it's totally fine to have kid characters be a part of that message.