I already killed then twice, so far so good. Then a dialog opens with the only option being "Yes" Then as soon as I press "Yes" the game crashes.
I have experienced that in a past mod with the slavers. For me it seemed to be something with the dialogue from the verb gaurd once you teleported in to verb after you say yes to the child. It happens real quick and you may not notice it, but my crashes all involved teleporting in with a summon mob and/or dominated mob and the gaurd captain seemed to try and initiate dialogue with a summon mob and not a character in your main created group. On my third try, I killed off the summon mob before the end of the slaver fight and did not crash.