I think I will put a space heater in there with them, at least at first.
Just make sure you're being REALLY REALLY CAREFUL about using/securing/monitoring it. Over in the Michigan thread (and it's a whopping 9 degrees here this morning) the standing consensus is to avoid heaters, period. If you have an unheated garage or basement or breezeway/mudroom where the outdoor temperatures are moderated by the building I would put them in there for a week or 2. (I don't have any of those, so I understand how this can be an issue, and it's why I don't hatch between October and March.) I'm sure you've considered it, but it's always a good reminder, especially since a lot of people read but don't post.