12' should be fine to winter fish. I am sure you will get better answers than mine, but my 20 acre pond isn't much deeper and it seems fine with wintering fish. The concern in your case might be making sure that it is full and actually 8'+ deep going into winter. It will be nice if you guys can use a well to keep it full, esp. since we are in a drought and you may have a tough time getting enough runoff anyway.
You may want to go through a winter and make sure it holds before putting too much $ into stocking.
