My very first broody duck, a runner, sat for 4 days after hatch started. I've had hens get up after the first day too. I usually go out after she's left to see if any leftover eggs have pipped. I've brought in and finished hatching a couple. In my experience, the eggs that are left don't usually hatch. I'll go out and clean out the nest, sometimes put in new bedding, so that mom has a nice nest to start raising her babies in. Usually, they'll keep them inside for a day or 2. Watch your other adults with them too. Drakes and other hens may not appreciate the new invaders.
I usually put food/water out the day after hatch starts. Remember to offer day old appropriate feed, feeders and waterers.
Since this is your first time, and possible the duck's too, try to leave her to it as much as possible. We all want to get a look but I find that this can stress out mom and when she is trying to protect her babies, she can accidentally injure them by stepping on them. Keep an eye on her for the first few days. Not all good broodies are good mommas. I've had hens abandon babies after a few days.
Congrats! Post pics when you can.
