Colubrids such as corns, rats, kings, gophers, etc, will not suffer in cool (but not really COLD) temps if their stomachs are empty. Keep them in the warm cooler as described, and take them out for a short time while handling them if indoor temps are a bit cool. It should not cause a problem for them.
I would be more concerned with boas and pythons. The cooler would also work well with them, though. And if they are wrapped around your arm or shoulders when out, then you will provide a "heat pad" for them. Or, you could plug a heat pad in on the display table so the animal can sit on it while being displayed in a cool room.
I am actually more concerned with overheating during the summer. Heat kills WAY more quickly than temps that are too cool. The cooler in the summer (with cool packs) may be even more important than it is in the winter, at least for colubrids.