Congratulations to your son. I retired in 2012 after 24 years and really don't miss it often, but I still live in a GI town so kind of still a part of it.
The good thing about a military pension is it comes while you're still young enough to do stuff and allows a cushion so you can do something you like rather than something that stresses you because you need to pay the bills. Guys who retire and do nothing afterwards tend to die young. Make sure he finds something rewarding to do that keeps him busy.