As to killing children - I was under impression that tiefling children are unkillable (I remember people saying why we can kill goblin children but not the others). But either way, children are NPCs, we get to attack NPCs and children are one of them. If on the other hand after completing a quest chain player would be rewarded with lengthy cutscene of our hero killing children in different ways - yeah, I would be pretty disturbed that the game seems to think I would enjoy seeing it.
