Heroes don't kill children. Alignment doesn't matter.
In Kill Bill Volume 1, after the bride kills Vernita in front of Vernita's daughter Nikki, the Bride tells Nikki that Vernita had it coming to her, and if, when Nikki grows up, she can't get past the killing, she should come find the Bride. 'I'll be waiting,' the Bride promises.
So here is an example of a hero knowing full well that the child may grow up to be a problem in the future.
In Kill Bill Volume 1, after the bride kills Vernita in front of Vernita's daughter Nikki, the Bride tells Nikki that Vernita had it coming to her, and if, when Nikki grows up, she can't get past the killing, she should come find the Bride. 'I'll be waiting,' the Bride promises.
So here is an example of a hero knowing full well that the child may grow up to be a problem in the future.