Opinions on adult Dobermans, Rottweilers, or GSD's from shelters for households with small children?

Normally I never recommend having any dog with a child under the age of 4, but it sounds like your little one is "dog-trained"....lol. Why not stick with the small breed until your child gets a little older? If you are still determined to get a Dobe, Rottie, or GSD, go to the breed rescue groups that test the behaviors of their dogs before re-homing them. I would not trust a shelter dog with a small child, especially a dog of these breeds. Most of the time the shelters have no idea why the dogs were turned in, other than what the people tell them.... A legitimate breeder would refer you to others that have gotten puppies from them, so you might consider that avenue also. In your case I would definitely go with a puppy, but I' d do some serious research about any breeder you are interested in and get a tight written contract about what the breeder will back up and what they won't.