You've also asked about heat. More important than heat, is to somehow make your coop draft-free. No matter how much heat you give them, if they're in a draft, they could get sick and die. I live in MN where it gets down to -20 to -30 for days at a time. My chickens do not have heat in their coop. It's draft-free, ventilated, and not insulated. You have BO's - they're pretty cold hardy. I'm not sure what kind of chickens your grandpa had that froze to death. Were they very young and not fully-feathered? That's the only reason I could imagine a chicken freezing to death in NC. I'm glad you and your mom are getting things worked out. I am curious, however, as to why you don't want them laying in the winter? I think if they're going to lay, they're going to lay whether you give them layer feed or not...
