I second
@GennyB response. They're docked very young so wouldn't know which pup would go where at that point so leaving one undocked anticipating it would be a match for you family would be very tough. They're cropped older so maybe a higher chance but most of the breeders I know/follow still wouldn't leave a dog natural.
I understand your reasons for being hesitant to adopt but from what I see, there are PLENTY of adoptable dogs who are savvy with children. Most dogs in rescues are there because of something that happened within the family (divorce, health issues, time, moving, etc.); not because of issues with the dog. If you start checking out rescues, find one that is specific to Dobermans. They will have you fill out an extensive questionnaire and may even do a house visit. They're pickier about homes than some breeders because they want adoptions to be for life. Just like a reputable breeder, a good rescue will take a dog back if it doesn't work out.
My last boy was a 3 year old, docked but uncropped rescue who was raised with children which he ADORED. The family felt they didn't have the time he needed to devote to him.
Good luck in your search!