I haven't seen any DTD stores and restaurants offer a military discount, but I haven't asked at each and every place. Hopefully others have a better knowledge!
Edited to add: Don't forget most local hotels offer a military discount, and there's Military Salute tickets for the parks!
I don't know about DTD locations, but Ghirardelli's inside DCA offers a military discount. A CM asked us about it this past weekend. And I think Pizza Press on Harbor offers a military discount, too. Certainly worth asking about wherever you go.