You guys are taking this well beyond the thread's intent. Should the kids be killable? That is the question.
My short answer is "Yes."
A slightly lengthier answer is "Yes, although any resultant repercussions will be lessened or absent if the juveniles are monsters."
By the way, I only added that extra commentary as opposition to two particular viewpoints ->
1.) Some folks objected to the killing because they - in essence - view goblins as funny looking humans
(with all the attendant consideration afforded to human beings).
2.) Other folks objected to the option because they're worried about
(uninformed and obdurate) spectators who will clamor for the game to fail.
Yeah. I know. I just saw that we were detaching more and more from fantasy and moving into real life and world stuff and politics and I can hear Composer now just chiming in as s/he shuts down the thread.
I honestly can't believe I'm even involved in this discussion. I remember when I first played dark forces 2 and you were able to kill civilians in that game. It really messed with me the first time I accidentally threw a grenade and killed some random pixelated lady who was walking by. I gained Dark Side points for accidentally killing civilians, and I felt all guilty and had to reload.
Then I played with my wife and she laughed. She asked me if I realized that they weren't real. They're just dumb pixelated representations of human beings. Then she shot one in the head just for fun and laughed her butt off. She told me how she would never actually hurt anyone in real life, but because it's a dumb stupid video game she had no problems whatsoever just blowing the crap out of civilians.
Regardless of how you view make believe goblins and tieflings, at the end of the day none of it really matters in terms of morality because they aren't real. We could also argue all day long until the world blows up whether goblins are actually evil as a race or not. There's no way to ever win that argument because in all reality they don't exist.
That's why I was trying to bring it back to how the DM is representing them in this game. They are evil. End of story.