If you've never eaten heritage chicken before, do know it will not be like supermarket chicken. Those chickens are butchered at 6-8 weeks of life. 6 months is usually the max I have seen suggested for a chicken you plan to eat, because they get pretty tough afterwards. It will already be a rather tough bird. Some suggestions:
"Rest" the birds in the fridge for a couple days before freezing
Use them in a slow cooked stew or a crockpot
Don't try to roast or BBQ, you will likely be disappointed
These have less meat, don't try to feed a whole family with just one bird
The flavor is amazing. We cooked our first rooster (5 months old) in a crockpot the other day. Medium setting for about 6.5 hours. Turned out pretty tasty and fairly tender.