Lots of things to keep in mind with ducklings. Regular chicken feed is not very suitable for them, as they require much more niacin than chickens. Chicken starter can be used if you properly supplement niacin into it with nutritional yeast flakes or some other niacin source. The most highly recommended feed by veteranarians for ducks is Mazuri waterfowl feed. Your waterer you have there might work for a few days, but ideally you will need a water dish that they can completely dip their heads and bills into, without being able to swim in. A lot of people use plastic containers and cut holes in the lid providing a good hole for the ducklings to drink.
Not sure if you got them sexed or not, but if not you might need to be ready to rehome a male or 2 if your male/female ratio is off. You will want a minimum of 3 females per male, but it would be better to plan for 4 or 5.
I'm sure others will have more to add, but they are absolutely adorable and I wish you the best of luck with your new babies!