The difference between cracked corn and whole corn is the bird gets the full use out of a whole kernel, germ and all. When cracked they might not get the whole of the corn, but I don't think it makes a big difference. I feed both. Some like it whole, some like it cracked.
As long as they are healthy, fully feathered, and acclimated they will be fine. They may fluff up their feathers, or sit close together to share body heat.
Glad you aren't using heat, healthy chickens don't require it. The idea behind corn is it is a slower digestible food compare to rations and the act of digestion produces some internal heat throughout the night, not sure if it's been proven or not, but must be something to it for it to be around...