If you have a car, head out to the National Harbor - I think you can also get there by water taxi. They have all the usual places to eat there plus some really unique ones. There is also a Gaylord hotel which will be getting all decked out for Christmas with a singing Christmas tree, artifical snow, etc.
Another good bet - take the red line on the metro to downtown Silver Spring. Lots of good places to eat there - both unique and familiar, and the prices will be much better than Old Town. There is really cool stuff in the lobby of the Discovery TV HQ.
As for attractions, you will be busy with the freebies - the Smithsonian, Air and Space, the monuments, etc. If you want to spend some money, the Spy Museum is pretty cool and so is the wax museum.
My kids HATED the Newseum. It was way over priced, plus, it is very depressing. The news is usually depressing. It is interesting for adults, but the kids begged to leave.
The national gallery of art is cool and has a great cafeteria downstairs with an interesting light tunnel that kids enjoy.
There is also an aquarium in the basement of the commerce building that is cool.