7 month old cocker spaniel barks at new owners

Question
The 7 month old male cocker spaniel was given to my father just a day ago. The previous family couldn't handle the dog barking at strangers. The dog would chase the mail man and would even chase and bark at cars. The previous family would leave the dog home alone long periods of time. They realized they couldn't give the dog the time and attention he needed so therefore they decided to give him away. We have him in a kennel because we don't know what he would do since he doesn't know us. When we try to feed him or just get close to him he starts barking and growling at us. We don't know if he will nip or bite, we haven't tried petting him because we know we are strangers to him. Once we move away from him he would lay down and would be quite. I have three boys (ages: 12,7, and 3) and my 3 year old is so scared of him. My questions are: What can we do to break the dog into his new home? What can we do so he won't bark at strangers without taking him to obedience training?

Answer
You're not equipped to handle this dog.  He's only 7 months and if given the proper attention and training he'll be fine. But with no obedience training he won't be.  And he shouldn't be around a 3 year old child at this point.

Go online and find the nearest Cocker Spaniel Rescue.