Can't tell you how jealous I am of your land and outbuildings :) I'd be beside myself with what to do as well! I'd want to have a woodshop again for sure ... if not, I'd do chickens in one, and other poultry or goats I the other!
Did you say you have two such structures? Would be good if you're looking to do laying hens AND meat hens. Better if they are separated as they'll have different feed requirements. For your laying hens, more forage the better. I can't say what you would need to do to sanitize the earth, but if...