I have heard there are many more variable options now. Very few 4 year scholarships, some 3, some 2. Doesn't cover room & Board. Monthly stipend. The fact the stipend is now $500 is great; was $100/month back in my day
Typically you owe 4 years on active duty but that was when I had full four year scholly. If they only give you 2 yr scholly kind of sucks to owe 4 years.
Air Force tended to prefer a technical engineering or science degree; much harder to win the scholarship saying you want to major in business or history but that could have changed.
Good luck to your son!