Most if not all child offenders have, by all accounts (often including their own), done terrible things.
However, the fact of the matter from legal, psychological, and statistical perspectives is that the vast majority of them are legitimately mentally ill individuals who need help.
What they have done is not right. Many of the wounds they have caused will never heal. They should probably be kept away from children and even if they are not, parents have a right to demand to know where they are and to keep their children away from them.
Nevertheless, in a free society that values human rights, you cannot kill someone for doing something that was completely affected by something they could not control. You may force them to undergo treatment, you may keep them somewhere where they will never have the opportunity to commit these crimes again, but you cannot kill them.
However, if they are not a victim of mental illness (a very small minority of child offenders are not) and they decide to violate the rights, security, and safety of innocent children… may God have mercy on their souls because the criminal justice system in this country certainly should not. If any crime is worthy of the death penalty and was performed by a man or woman who rationally and intentionally, with a relatively clear mind chose to perform such heinous and unspeakable actions to a party so innocent and indefensible… this is definitely the one.