Can't you just send those two disciples away in the inital conversation? I normally don't bother with them, kill them (I have not much tolerance for zealous people) and then go into the cave, talk to mum (maybe steal the egg and the Oakfathers Promise), then leave them and get the owlbear cub in the goblin camp. That way, you don't have to risk them dying in the caves, if you want to keep them alive.
