If you are going to go for a delay on the hearing anyway, and reading of your son's inability to concentrate after a short period of time talking, it may be beneficial for him to get a psychological/psychiatric evaluation for his file to document this...his regular doctor should be able to refer him. DO NOT allow Social Security to send him for an evaluation at one of their quack psychiatrists, or you can be sure they'll manage to put something unhelpful in his file. The ALJ has wide latitude within Social Security to "believe" or "disbelieve" anything he wants based on anything he wants, including anything that your doctor has provided.
If the ALJ issues a denial, you can appeal that. There are also two or three levels of appeal, within Social Security, above the ALJ. Each time you appeal, expect it to take another year or two. Once an ALJ issues a denial there is a strong tendency within Soc Sec to stick with that decision no matter what...government employees don't like to admit mistakes. When you've exhausted appeals within Social Security you then must take your case to Federal District Court. You can also appeal a District Court decision. Under such a situation 10 years to get benefits wouldn't be out of the question. Soc Sec also limits lawyers' fees to something like $5-6K, but once you get to Federal Court the court will decide what is a reasonable legal fee, and it will be much higher. Most lawyers work on the basis of no-win, no-fee, with the fee being taken out of past due benefits.