Are you going to be keeping your ducks and chickens together? If so you'll need some more nest boxes and know that ducks are wet. Ducks don't roost, so they should have an area to nest or snuggle down in (NOT a nest box and definitely NOT under the roost area).
Ducks are extremely wet, and messy. They need water to swallow their food, thus they dribble water and food everywhere. They do better on straw or wood pellets than shavings, because shavings get soggy so quickly.
Because they need water to swallow their food and to breathe, you need to provide water with food. No water=no food. They need to clear their nares (nostrils) and wash them with water too, so they need an area to dip their bill in.
Ducks and chickens generally get along well, but I suggest providing an area ducks can escape too. An ambitious rooster may try to mate with the ducks, although he won't fight with them. Ducks must be introduced to the flock like any other chicken.
Ducks in general are really happy and friendly. They are easily won over by treats. Are you starting with babies? If so, make sure they have their niacin requirements met. Ducklings must be started on duck grower or flock grower (between 18 and 20%). If started on chick grower, you'll need to provide additional niacin by giving them brewer's yeast.
Ducklings must be handled a lot if you want them to be friendly. Don't let ducklings swim until they are fully feathered unless you are going to be drying them off afterwards- otherwise they can become waterlogged and drown or die.
If you want a medium (6-8 lb) duck breed that is friendly and lays well, I suggest Welsh Harlequins, Khaki Campbells, Indian Runners, or Cayugas. All are pretty, and all have good personalities. Welsh Harlequins are the best layers of those breeds at 300 some eggs per year.
Pekins are friendly but only lay 180 or so eggs per year. They are friendly, white, and fluffy, but larger at about 10-12 pounds.
