I too would be afraid to let them out in a big room. They will be really hard to catch and harder to tame if they have too much space to run from you.

I would continue as you are, trying to touch them and play with them in the cage. It will surprise you how quickly they get used to you. Maybe feed them wet food from your fingertips. Soon they will see you as the bringer of good things and you can start to handle them. When they get comfortable with being touched, you can let them into a small room with as few hiding places as possible.

They can be extremely quick and hard to catch when they are still afraid of you.

I truly wish you Good Luck in this endeavor. I have a feral that is older and has been at my house for two months. Still can't touch him, but he'll accept treats from my hand.