The giants ants are going to be real trouble. If we engage them it's going to be a fight, no matter the plan to lure them to fight the kobolds. I am not sure what type of lure we could use. Honey? We would need a barrel.
I am wondering if we continue the excavation of the ruins would that cause havoc for the creatures below. There are already pot holes to work with what if we just continue the process. Kobolds live underground for a reason, so what if we take away that protection and expose them to the elements. If they like the safety of the dark let's take that away.
It is not ideal for adventurers to become construction/demolition workers but the frontal approach has not worked. We need to come at this problem from the side. What would we never do in a game?
I still think going back to town is ideal. Pick up new supplies and come back armed better. More supplies, more shields, more knowledge... It could not hurt us more than what we have been doing now.