How to check under broody without causing problems?

[Schrebergaertner]

We're hatching our first clutch with a broody. Yesterday was day 21. Yesterday morning we took her off the nest to eat, drink, and poop, and sure enough, there was one pecking out and another with a crack starting to show. A couple of hours later we checked again and the one had a big hole and was peeping a lot, but it looked like the rest of the shell had been smooshed down a bit under mama. We went back again a couple hours later and the chick was dead. Almost all the way out of the shell, it was clear it had been smothered.

So I went back and read lots of threads about smothered chicks under new broodys, and we decided not to disturb her anymore, since I guess the in and out can cause the problem, especially with a new mom. This morning we can hear at least two peepers under her. If she's inexperienced and likely to smother these too, even if we don't move her, we want to do what we can to save the chicks. However, if moving her is going to do more harm than good, I want to leave her alone.

So is there a way to check what's going on under her, but minimize the danger of her squashing them when she gets up and down and moves around? And if we have to just leave her be (hard as that is, with all the excitement), how long do we wait to assume all are hatched that are going to be?

Thanks!