Unfortunately, the article you read raises hopes much more than is warranted. This CRISPR technology is a major breakthrough for laboratory science and should speed discovery of many new therapies, but it will not work directly in humans. At best, the direct therapeutic applications will involve stem cell's engineered in the laboratory and then reintroduced into patients. I'm very sorry to say that I cannot foresee any direct application of CRISPR that could help your son's condition. I tried to explain to the reporter that CRISPR could not be used in humans directly, and I did not see his article until it appeared in the paper. It is not just an issue of safety but simply that it cannot be used to repair genes in millions of cells within a person's body, there is just no way to deliver the enzyme to all the cells. Even if we could, the enzyme makes many mistakes for each correct modification, so it would very likely cause more damage than good. I don't know if we will ever solve these problems. It is very difficult to repair the genes in every cell within a person.
I sincerely hope for the best for your son, I can only imagine the heartbreak that you and your family are experiencing with his diagnosis. If his deletion is in frame perhaps he will preserve some gene function. I'm sorry I could not bring you better news. CRISPR will speed laboratory science related to muscular dystrophy so it is a very good thing, just not an immediate cure or therapy.