So sorry no one has responded yet! I just found your thread myself. Since no one knows exactly when the eggs were put in, nor what effect a week without heat might have had, it's impossible to tell when they are supposed to hatch. I can only suggest a couple of things:
1. If it has externally pipped, and goes 24 hours without any progress, then it's time to assist the hatch. Don't jump in too soon - Often they'll pip, chirp and rest over several hours or a full day before making the final push to zip.
2. You can make a "safety hole" in the air-cell end of the egg, to help it breathe and to see what's going on in there.
3. The one that pipped yesterday, but was still when you got home - yes, go ahead and assist the hatch. If it's already dead, then no further harm will be done. Depending on how long ago that partner egg pipped, you might assist that one, too.
Oh, and welcome to the forum! Happy you joined. This is probably the best place on the internet for chicken information and is full of very helpful members. Looking forward to seeing your step-daughter's chicks (whether these few, or the next batch) grow! Please keep us posted.