First question would be, what does he want to do in the Marine Corps?
Keep in mind the Marine Corps has a very tiny budget compared to every other branch of the military(maybe the Coast Guard is close). Due to the tiny budget, the equipment is typically crap that we had. I started to realize that at my first duty station at Kadena AFB. I got to compare our Navy/Marine Corps junk to the Air Forces' seemingly brand new EVERYTHING, lol. I remember one time telling some airman about where our shop was at because he had no idea any Marines were stationed there. When I told him the shop, he thought it was a DRMO yard, basically a military junkyard. I just laughed. Just about everything I had issued to me or equipment I had to use was falling apart aside from my uniforms and the last barracks I lived in.
So my background, I was enlisted from 1998 to 2003 in the Marine Corps as a 6075(6074) Air Separation and Cryogenics Technician. Went in as a Private got out as a Corporal. I can tell it from the air winger side of things.
Originally I was planning on going into the Air Force because I grew up being absolutely in love with military aircraft. A friend of mine in high school was already signed up for the delayed entry program(DEP) and both of his parents were former Marines. He got me to go talk to his recruiter and I got sucked into the don't be a dork in the the Air Force, "We have the best uniform", and "We are tougher" stuff.
At the time(1998), you could sign up for 3 general MOS(job) choices. My three choices in order were:
1. Aviation Mechanic w/ Secret Security Clearance
2. Aviation Mechanic
3. Aviation Ordinance
I ended up with the first choice and never did anything that required my secret clearance for anything that I know of. So basically I got what I picked.
I'd say 70% of most Marines(in the air wing) always joked about being tired of the Marine Corps in some form. It seemed like the status quo. The new and shiney "I'm a Marine" wears off about a year in. But in all honesty, I think it is a great way to learn budgeting money, living on your own(although having a barracks roommate, lol), respect for others, hard work ethic, and of course discipline.
When it came time for reenlistment or getting out in 2003, I was planning on getting out and switching over to the Air Force. However, the Air Force wouldn't take me at the time because I would of had to go back through a tech school since my MOS didn't transfer over equally.
At any rate, would I do it again... Absolutely.
Would I suggest it to someone... Absolutely.
Would I have my own kid do it... Absolutely(but not if it was my daughter, no USMC)
In all honesty, you will learn discipline in all branches of the military, the biggest difference is how tough Marines make it. Its not as much of a physical toughness as much as a mental toughness. I think the biggest difference is having E36 M3 equipment.
With all of that said, I would say your son has the smarts that he should be an officer. No matter what branch, he should be an officer. If he has a choice, stick to the aviation side of things because the career paths are much better.