The one and only time that I hatched I peeked once and there was a dead chick under there.... Then later I found a live one.
I would just run your hand under her and make sure that they are all alive.... if not you need to remove the dead one and dispose of it before it begins to smell. I know that this is a hard concept but it is important.
I always did the 'run my hand under there' thing, but I've been lucky and not had a mean broody (yet). You'll see them peeking out in a day or two, usually. Might have to at the right time to catch them peeking if it's cold, though.
I'll have to go peek. So you don't have to worry about shrink-wrapping or other stuff like that since you have a mama hatching??? I didn't want to peek in case it messed up the humidity/temps under mama. Don't want to kill any babies just because of stupid human mistake!!!