We did a hatch of 4 call ducks with mama duck indoors. It definitely requires 24/7 attention.
We fenced them off in a corner of the room, where they would stay for a couple hours at a time. Then they'd go outside for 30 minutes of supervised play, then back inside. Once they were put to bed at dusk they would be quiet all night until the crack of dawn. They got used to being herded down the hall and out the door, and mama helped us by leading and calling them. She knew how to get outside already so she was a big help, but the little ones would still need help finding their way sometimes. You may find it easier just to put everyone in a carrier to take them outside, but we had too much fun watching them figure it out.
For their pen, if there is an inch to squeeze through, ducklings will make it out and then stand there peeping for mama. Definitely make it a very tight enclosure, with at least 2 feet tall walls. I had to change the bedding daily. Several layers of newspaper with straw on top made quick work of that. Just fold up the paper, toss, and replace with new.
For their food, I used a large flower pot saucer and put a shallow bowl in the middle. Their food went into the saucer and the bowl in the middle had water along with some rocks in it so they couldn't tip it over, (and they did try). I would refill the water and let extra spill out to moisten their feed. I had to top up their feeder every couple hours. The set up worked well being circular, so they could all find a spot to eat (though the best spot apparently was to be standing in the water bowl).
After the first week, we even had daddy in with them for a few nights (he got so lonely and after watching his behavior around the little ones, we trusted him). They would all snuggle down for the night and be up bright and early, quacking to be let out.
At week 3 we put them outside in the big pen for good. The weather was warm and they did just fine.