Just let the player do whatever he wants. Why is everybody rolling on their back for a couple of pixels on the screen. Its like , killing a 18/21 years old male human is okay, but killing a teenagers goblin isn't, are you for real?
Also, its okay to kill a village, but its not okay to kill some NPC because they appears younger? Uh? What about gnome and dwarf , then? They may be as small as children, but you'd happily slaughter them just because they have a better armor class, an axe, and lived a few more years.

If it's what it's takes to save the world, then the world doesn't deserves to be saved - Geralt