Either that would be rewriting history, which would be a horrendous crime on the scale of multiple omnicides (or even worse, if we're wiping out the whole Universe), or we're just creating alternative versions of the children in alternative timelines, leaving the originals behind. And if the timeline can't be tampered with at all, then it's just impossible, because we'd already know it would happen. Or maybe we're working with more complex off-road alternative timelines within a larger unchangeable meta-timeline that cause themselves to disappear from the timeline due to a future event returning everything back into the status quo ante chronofuck, which is also pointless.