You could keep the mother and father, and the additional females, maybe 1 more male. The only thing about having them together is the Father and his son may have dominance issues, and then maybe the issue of inbreeding with your ducks. If you kept the Mother Father pair and then the two females, you could get a drake from a different breeder, and sell the rest of your drakes.
Or keep them in a Bachelor Group away from the Females.
I personally would keep the 3 females, the older male, and then have 2 of the males in a bachelor group( One for breeding and one for company).
And then at some point buy 3 or 4 females for the male(s). That would reduce risk of inbreeding, and let me keep some of my original Juvenile Drakes.
You could also keep your set up as it is but downsize the Bachelor group from 6 to 3 then get 6 Females and keep the Mother, Father, Daughter pair and Bachelor pair away from each other.
Im not sure if this was any help but let me know how it goes.