Lot's of good advice so far. On of my tours in the Navy was as a "detailer" in the Bureau of Navy Personnel. Essentially I managed the careers of over 400 naval officers, making sure they got the right jobs and education to position themselves for success.
Since I was detailing Aerospace Engineering Duty Officers (guys and gals that that are either pilots or NFOs who have been assigned to navy space, acquisition, engineering and flight test activities) the group was heavily laden with engineering talent.
My first question when the graduate degree question came up (over 90% of these folks will get them), was, "what do you want to do, what makes you happy".
Some engineers hated acquisition management and preferred to stay in space or engineering activities. I would suggest a tech management degree, Sys Eng degree or a follow-on degree in their engineering discipline (aero, EE, Software stuff, etc.).
For non-engineers I would push for a 'soft' engineering MS like Sys Eng, IM, etc.
For those with an engineering undergraduate degree that were open to a management track the only choice was an MBA, finance or tech management MS.
While the above was applied to naval officers, we all retire at some point and I felt that a broad education in various area would help them post retirement.
Hope this helps
