The ladies will be mean if the drake is around. I am pretty sure ducks are middle schoolers who like the same boy. But, take the boy out. . . Besides, he cannot be with the ducklings until they are four months old or he could injure them by mating with them. They can get used to the girls...
I found that the girls are much faster to except the new comers than the boys. Personally, when you are ready to put them together, I would lock up the drake and let the girls figure it out. After a couple of days or longer if you start before the girls are of breeding age, try them all together.