Just let us knock them out, but not kill them
That is a flagrantly absurd idea. In an age where realism (and "realism") is treated as sacrosanct and "darker and edgier" themes are still enjoying immense support, the inability to kill a mortal being that just-so-happens to be on the lower end of the age spectrum is going to stick out like the proverbial sore thumb. Program in (appropriate and reasonable) consequences. Hell, introduce an Alignment/karma meter. Whatever L does, it should be anything but
that; having non-critical NPCs who would otherwise be susceptible to damage instead be inexplicably immortal is catastrophically immersion-breaking.
No. Let us knock out the tiefling children so the goblins can take them alive and put them to work doing slave labor... or fatten them up and eat them. That's much better.
Look. Let's put it this way. It is fantasy. It isn't reality. In D&D, usually goblins are vicious, malicious, terrible monsters. However, if in your D&D play sessions you make goblins just another race that aren't this way, that's fine. You see them as another race. However, this is not the goblin tribe that Larian is presenting to us. The goblins and their children are vicious, malicious, terrible monsters. Larian, being the DM, has the right to present them as such.
And as such, they need to be wiped out. All of them. (Meant to be said like Darth Sidious in Phantom Menace.)
Imagine you are a mercenary in Aradin's adventuring party. There's this dwarf named Brian who is jovial, fun loving, loves food, and he is as greedy as sin. He's got this great treasure map, and he's telling you all about how rich you're going to be some day. You guys all go into this temple to try to find the treasure - and find vicious, malicious goblins there - TONS of them. They swarm you. They capture you and Brian and a few others. You're lashed to a torture rack along with some other guy you barely know, and there's poor Brian.
"Hmmm," says one of the goblins, and he pokes Brian in the gut. "Fat and juicy. Eh boys? Looks like 'e'll make a GREAT suppa for at least a few o' us."
Goblin kids nearby start laughing like gremlins from the 1980s movie. "I want at least a finger. They look like sausages."
"I wanna chunk oh the breast. Please Spike! Please! He looks SO tasty."
Then you watch as they kill your friend Brian right in front of you. Then they chop him into pieces and carry off his parts to the cooking fires. And guess what? You're next.
This may be my head cannon, but it sure does seem more like the goblins in BG3 than what maybe some on this forum are thinking. Evil. They are evil and their kids are evil. Put yourself in the shoes of the victims of this fantasy world. This is not like Trandoshans in Star Wars who come from a warrior race - some are mean and terrible but some aren't. This is goblins who traditionally, and in BG3, literally capture and kill people and enslave them and eat them, just like poor Brian who is found roasting on a spit when you enter the goblin camp.
That is a FAR cry different from the tiefling children who might smart mouth off to you here and there. They are not really evil. They are just a bunch of smart mouthed punks who are actually scared to death but they're trying to be all tough because it makes them feel better.
All that said, if Larian wants to create a true RPG, they'll allow PCs to either knock out or kill either group of kids if the DM (Larian) sets the stage for the PCs to do so. Again, if some brat tiefling is going to turn an entire grove of dozens of people against me, both tiefling and druid, if I'm good, I - me the player - will make the decision to knock them out or grapple them to the ground rather than kill them - but if I'm evil, I - me the player - will make the decision to kill them off because they're nasty brats and I can't stand them and they are now threatening my life. If they're not going to allow players to knock out and/or kill the kids, don't put players in the position that they are going to basically be screwed if those kids get away.
Likewise, with the goblin children, you have the option, provided by Larian, to simply knock out the kids. You don't HAVE to kill them. It's your choice. If you're evil and you just don't care, death be to the goblin kids. If you're good and your conscience says, "But they're just kids," Larian has given you the right to decide. If you're good and your conscience says, "These are monster kids who will grow up to be people-eating monster adults. Best to just kill them because it would be less cruel then letting them live without their tribe, parents, etc." Then that's up to you, the player, to decide.
There should be no difference between the two scenarios regardless of whether goblins are evil or not.
