Just because this breed fits into your criteria (or at least, certain mixes are common in some areas that will have short hair), and because they are an easy breed to fall in love with, I just want to issue a lesser known warning about Australian shepherds. They are a geat breed. They can be some of the most loyal and child-devoted dogs around. But, they have a high rate of epilepsy. Typically, this is a manageable medical issue, however, sometimes, this includes an epileptic condition that leads to something very similar to how 'rage syndrome' expresses in breeds like cockers. I adopted a beautiful male Aussie/cattle dog mix who was just over three years of age (3 years is typically when this starts expressing...I am sure it is why he was in the shelter). It is degenerative, and he progressively got worse. Medication helped his grand mals, but it did not help his petite mal seizures tha altered his behavior. In a blink of an eye he would go from happy and waggy to literally trying to tear off your face.
Basically, petite mal seizures are not the convulsive seizures most think of, and may never even be noticed as they may only present as something like staring off or blinking oddly. In his case, the petite mals effected a region of his brain that caused intense fear and aggression that was npredictable and rapid. He was a sweet, loving, intelligent, wonderful dog. It was the hardest thing I have ever had to do to eventually euthanize him once treatments failed. I would be particularly wary of Australian shepherds who are three years of age in shelters. I have unfortunately since heard the same story from many an Aussie owner. There may be breeders out there carefully breeding aay from this, or unaffected lines if you do fall for the breed. An older Aussie (probably at least five or older) should be in the clear for this particular problem. I just wish I had known about this before we adopted. It took months to figure out what the problem was when aggression began appearing more and more frequently.
That said, our other shelter dog is the best dog I've ever known or owned (pure ACD). Don't mean to scare, just to inform. I think a shelter dog is a great, maybe the best, option for finding a dog hat will bond strongly to your son.
. It is especially helpful when trial periods are allowed by the shelter or rescue.