Firstly I would choose a medium to smaller dog breed.
You need to choose a dog that your son will be able to control when it is an adult.
If this is the family's first dog perhaps you should choose an easy breed like a spaniel. By easy breed I mean some breeds are stuborn and need someone with experience to handle them. Spaniels are one of the more gentle loving breeds that a young teen with little experience in training dogs can handle.
Please send them to puppy school as this will help to teach your son how to train his dog. Dog obedience school is also a great idea. Good luck and have fun with your new found friend.