In my good playthroughs I don't kill the goblin kids, I let them run away ( I deal with the three leaders first before freeing Halsin, so they can't really bring reinforcements).
On this tangent, in my Patch 9 plays, once I kill the Goblin leaders and return to the grove, Halsin is automagically freed. Maybe it was always like this and pre-Patch 9 I always proceeded on to rescue Halsin after killing the leaders.
