Personally, I would research the breeds that "Fit the Bill" of the purpose for the dog and the characteristics and personality that would best fit your son.
This is nonsense. There are more differences between dogs within a breed than between breeds. You want a good dog, get one from someone who actually knows the dog and doesnt breed them. The best dogs Ive known were mixes who were old as the hills. You dont want a dog that will grow up to be who knows what. You want a dog that is known, who is trained, who has years of good reputation with children. Just because you get a puppy doesnt mean it will grow up to be an angel who is perfect for you. Most dogs in shelters were bought as puppies. JS