I had a litter of 4 cocker spaniels of which I had homes for 2 of them before they were even born. Both of these homes decided to keep the tails on their puppies which was fine but they had to choose their pups before they were 3 days old so that I could get the others docked.
I found that slthough the puppies owners had to choose their puppies early they bonded really well because they knew their puppy for 8 weeks before taking them home.