I have a couple of points to make, because they bear mentioning:
1) A result in any one case does not guarantee that the results will be the same in any other case. Those people relying on the results in the OP's case might well find themselves in a different scenario.
2) Generally, students (basic training, AIT, tech school, etc) can get out of the military easier than can others -- for permanent party, the usual result seems to be court martial.
3) The BEST case for AWOL is a Chapter 10 case, which typically results in an other than honorable discharge. The WORST case is most likely a special court martial, 30 days brig time, and a bad conduct discharge.
If an OTH is awarded:
In terms of future repercussions: as long as the OP's son does not want a future in law enforcement, government work, or potentially politics (where the OTH is sure to be brought up), it will probably not affect him/her. If junior has ambitions for medical school, law school, or any other competitive schooling, it can be brought up again and can be a factor in admissions. Also, expect to disclose it and for it to possibly hurt for any other licensure by state or federal governments for jobs that involve the public trust (lawyer, stock broker, doctor, vet, pharmacist, etc). And a private employer CAN ask about it, and junior must report it or face termination for lying on an application. Similarly, junior can face adverse employment consequences. All VA benefits are most likely lost. I am sure, concerned mom, that you are aware that in accepting the Chapter 10 package, your son admitted that he committed a crime, right?
The nuts and bolts, however, is that this is unlikely to hurt in the long term. Most employers will not dig that deep even if it isn't reported. And most people do not pursue professions listed above (law enforcement, government work, politics, or other professions that require licenses).
The purpose of my post is not to dissuade people from turning themselves in. Rather, it is to encourage people not to break the law and go AWOL to begin with. I make no judgments about the reasons the kid went AWOL. But I do feel it is grossly irresponsible to state that this will have no impact on the kid's future, without knowing what he wants to do with his life.