Check out the army MWR website, or sato travel. My husband is in the Naval Reserve, and we've found no cruise discounts unless the military member is active duty.
We're doing Disney via Shades of Green this fall and buying discount park tickets at ITT where he does his drill weekends, then going on a 4 day Disney Cruise. It was all booked separately to get the military discount from Disney on the hotel and passes. They offered nothing for reservists/guard unless you're activated.
Wow, I see your post is over a month old, so you've probably worked this all out already. Oh well, it's written, so I'll send it.
Have a good time on your cruise.
Julie