I understand that retrieving the bodies of our fallen is traditional and honorable. I understand that on the mountain is an evil that should be suppressed. I understand that with knowledge of what awaits us, assuming the opposition repeats its tactics, we should be able to achieve a cleaner victory than in the prior expedition.
The problem is the assumption that the tactics will be repeated. If he is capable of learning, he could activate the lesser lower skeleton force when we are half way through the lower catacombs. This would leave us pressed forward and back against numbers we cannot handle. I do not believe we should assume this opponent is incapable of learning from mistakes.
It might also be, that if we have awoken a threat to the town, it might be proper to fully inform the individual with responsibility to defend the town, and with the force to cleanly remove the threat.
We might consider alternate approaches. Might we clean and bless the catacombs from the bottom up, putting the undead into final rest and leaving nothing behind us? Is this possible? Is it possible for us? If the response is to awaken the hoard and to push us back out the cliff entrance, can we contrive a clean escape?