If you do not wish to cull them, why not build them a small wild-like habitat, make it a retirement pen. Wouldn't need to be much, maybe a three sided (and roofed) area a couple feet wide for them to get out of weather, and a run area with grass, sticks, etc. in. Since you know you won't be putting any chicks in this cage you can use chicken wire (I find the plastic type to be less expensive and much easier to work with) and there doesn't need to be a real complicated gate system as you can leave any eggs they lay and clean them out once every few months or so. ?
Or post them on craigslist. Maybe someone will take them in as pets. I agree however with previous posters - you would not be "giving them their freedom" at this point it would just be neglecting to properly feed and house them until they die. :/