When our pekin ducks were 3 weeks old we went to 1 gallon plastic ice cream containers for both water and feed.
it was deep enough so they could wash out their noestrils. it is so funny to watch them dunk their heads and blow bubbles.
Our ducks are almost a year and still feed them out of the 1 gal buckets, but purchased 3 gal rubber tubs for the water, with a piece of folded 2x4 wire over it so they dont wade (and poop) in the water.
Chicken feeders dont work well because they scoopp their food rather than peck.
Whatever you go with, be very careful. I have had more ducks and geese drown than lost to anything else. At that age, if they get wet they are too heavy to float and will quickly die. So, whatever you use, make sure it's no deeper than they are tall... and better yet, put bricks in it for them to stand on in case they get in.