Make sure you do the happy hour at the ES for the free drinks and snacks. You'll be walking a lot in DC so relaxing is nice.
Preorder you and your wife a couple SmarTrip cards for the metro. It's cheaper that way and much easier to keep up with than the paper tickets. Metro is the easiest way to get around, I love how DC's is set up.
A few good suggestions:
If you want a quiet lunch with a good burger and beer, hit up Lindy's Red Lion. It's on penn avenue down towards GWU. Hole in the wall spot, but I love it.
I'm also partial to the Matchbox in Chinatown-Gallery Place for wood fired pizza. Get the prosciutto. Right next to the Verizon Center.
And on my last trip we chose The Founding Farmers for our nice dinner and damn if it wasn't fantastic. Also on Pennsylvania I believe but just a couple blocks from Lindy's. I had the Prime Rib. Order the kettle corn as an appetizer.
Attractions:
The two musts for me are Arlington National Cemetery and the Holocaust Memorial Museum. At ANC get out and walk around if you decide to take the tram tour. You'll regret it if you just hit the highlights. Really go and soak it in and let it hit you all the sacrifices those men and women made. Changing of the guard is unlike anything I've ever seen.
There's a neat lawn in from of the White House that my girlfriend and I laid out on. She read and I people watched. It's a great view though.
I recommend doing the memorials at night. Lincoln will just blow your mind with its size. Korean and Vietnam just have a different feel at night to me.
It takes weeks to see everything DC has to offer, but pick out what is most important to you and enjoy it. Take some bottled water. It's a hot city with lots of walking and vendors will bend you over.
