I think the biggest danger with young birds and the cold is "piling". For birds that sleep in a pile instead of roosting, there is always the danger that some will get suffocated. This can happen anytime of year when the temps get below what they are used to. I'm always nervous when the babies graduate to an outside pen. I have some juveniles out there that don't roost yet. I put a lamp in there as well as one of those seedling heat mats. Freezing weather....grrrr...and brrrrr.
Hang in there, Red! At least you can face head on what you have to deal with. It's better than the roller coaster of not knowing.
They are definitely piling...I worry about that too, it gets really damp and humid in the middle of that pile, it is an enclosed nest box with one side open. And i have worried about legs being broken and things like that. I have not gone outside yet...but I can see a few of the juvies out in the run, in the freezing morning temps, and they are pecking and running around so crossing fingers. There is no sign of the Polish and Houdans, but I can only see about half of their run from my back windows. I have preschool kids coming in right now, I should be able to go back there in a half hour or so and check them all out. Oh I am so nervous to go look!