If I candle them and put them back she will still sit right? We don't have an incubator and I would hate to lose them by messing with her nest. Also, after they have hatched do I need to take them? I don't really have a good way to separate the drake from the ducklings if they make it.
I can't predict how individual birds will behave, but I will tell you what we do.
The mama needs to get off the nest for a while at least once per day whether she wants to or not. Most do it voluntarily, but I've seen anecdotal evidence of ducks that will set on a nest and starve themselves to death rather than get off the nest. We had a buff Orpington at one point that didn't want to budge, so I shooed her off the nest at least once per day. She puffed, she hissed, she bit me, she fought as much like a tiger as a duck could fight, but she had to go for her own good. Once she was out, she enjoyed being out to eliminate, bathe, and just run around.
Once per week, we'd lock the pen so she couldn't get back in until we removed the eggs, candled them, then replaced them in her nest. She never seemed to know/care that we'd done that. It is a myth, at least with most birds, that they won't have anything to do with their eggs after a human touches them. I mentioned in another thread that I think that's something our moms and grandmothers tell us to keep us from messing with eggs in bird nests when we're curious kids. Just make sure you thoroughly clean your hands, arms, and anything else the eggs will touch before you do it so you don't contaminate the eggs.
I would not take the ducklings from her unless you want to hand-raise them. She would like to have her ducklings, and she's already attached to them at that point since ducks communicate with their ducklings before the hatch. The drake is iffy and something you can't predict until it happens. Watch that closely to see how the drake reacts. How that turns out will depend as much on the mom as it does the drake. Some moms will defend the babies, some will let the drake do as drakes do. If that happens with you, you're going to have to find a way to separate the drake unless you want to take the ducklings.