some ideas.  There are 17 total Smithsonian Museums in the DC area, plus the Zoo.  The most popular are on the National Mall, Air & Space, Natural History & American History.  Here's the Smithsonian home page: http://www.si.edu/
A major attraction right now is the new Giant Panda cub at the Zoo; unfortunately, it won't be on public display until it's a bit older (she's nearly 4 months now), so the best way to see her is on the Panda Cam: http://nationalzoo.si.edu/animals/webcams/giant-panda.cfm  But one neat thing at the Zoo is Zoolights, an illumination for the holidays that can be seen every night 5:00-9:00.
Another top attraction not part of the Smithsonian is the National Gallery of Art (http://www.nga.gov/content/ngaweb.html).  It is one of the 5 best art galleries in the US, is also free (all the Smithsonian Museums in DC are free), and has in its collection the only painting by Leonardo daVinci in the Western Hemisphere.
There are also the Capitol building (must go to the Capitol Visitors' Center in the morning and get timed tour tickets), the National Archives (original copies of the Declaration of Independence & Constitution), and of course the White House; the only way to tour the White House is to go through your Congressman's office weeks in advance.
Hope this helps.  As to restaurants, suggest you consult on of the social media review sites like Yelp, as their are countless good restaurants of most cuisines, Italian, French, Indian, etc.
Enjoy your visit!

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adults can often be seen outside ripping up bamboo to eat.
Foe top Indian food the best are The Bombay Club near the White House & Rasika with locations in Penn Quarter & the West End/Foggy Bottom; please note that they are not cheap.
Enjoy your visit!

Would be helpful if we knew what area you had in mind.  If in NoVA, than here are some suggestions.  

Pentagon City (Arlington):  Hank's Bar & Grill in Pentagon City Mall and there are a variety of restaurants in Pentagon Row (adjacent to mall towards the west) such, Thai, Japanese, Italian, Lebanese, Irish, American sports bar.  

Crystal City (Arlington):  There are a variety of restaurants along Crystal Drive as well as the underground from 18th to 23rd streets, such as, McCormick & Schmick, Ted's Montana Grill, Ruth's Chris, Morton's as well as various Italian, Thai, etc.  Also, on 23rd street both sides of Jefferson Davis (JD) Hwy such as Legal Seafood and variety just west of JD Hwy.  

Old Town Alexandria:  On King street east of Washington Street towards the river you've got about 6 blocks of restaurants too numerous to name.  I like the Fish Market, South Austin Grill, Virtue Union Street Pub, Columbia Firehouse, Hank's Oyster Bar, etc.  Just too many to name...best just to Google Old Town Alexandria and downtown restaurants.

Hope this helps!  

You certainly don't want to eat at any chains....you want a distinct DC vibe and experience.

Old Ebbitt Grill is near the White House and is frequented by many of Washington's personalities. Ben's Chili Bowl is the home of the Washington DC quintessential dish, the Half Smoke.  

The Monocle on Capital Hill is on the Senate side, and many Senators dine or drink there on occasions. If you can score a visit to the US Senate Dining Room through your Senator's staff, the Senate Bean Soup is genuine Washington DC.

The Mitsitam Cafeteria in the Smithsonian American Indian Museum is amazing for a cafeteria in a museum. You can graze across the American continent eating Indian fare, from planked salmon in the Pacific northwest, to the fry bread and buffalo burger in the Plains to the maple turkey in the northeast, all under one roof.

For slightly higher end restaurants, our nationally known chefs are Jose Andres (Jaleo, Zaytinya, BarMini) and Michel Richard (Citronelle), but our best restaurant overall might be CityZen in the Mandarin Oriental Hotel.

And we have world-class Indian (Rasika), Greek (Komi) and Thai (Little Serow) -- truly world class. Rasika might be the best Indian restaurant outside of India.

If you are interested in really good Indian food, in a very nice environment, you should check out Rasika on D Street between 7th and 6th in the Penn Quarter.  Short walk from the Archives metro station.

If you are interested in Italian-prepared seafood, you might want to consider Fiola, which is on Pennsylvania Ave a block from Archives station, but I believe the entrance is on Indiana Ave.  Weird D.C. street blocks.

Central, also on Penn. Ave and close to Archives station is very nice as well.  They have some French-inspired seafood there.

Hope this helps you out some?

OK

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Great suggestions - thank you!

before a bunch of major Government tenants moved out of the office buildings there.  There are a number of excellent restaurants there, including Morton's of Chicago, Ruth's Chris & McCormick & Schmick's seafood.  There's also one of Jose Andres's best, the Spanish Tapas place called Jaleo.  There's also a nice group of ethnic restaurants on 23rd Street across Jefferson Davis Highway.  And if you take the Metro to Pentagon City you can walk over to Pentagon Row which has numerous restaurants (including Lebanese & a good Irish pub called Sine), and a public ice skating rink.   As to night life, you can get on Metro (our subway system, Crystal City has its own station) and either head for Old Town Alexandria or downtown DC.  If you take the Metro to King Street station, Alexandria operates a free trolley down King Street all the way to the river every 20 minutes.

If you are going to be in Crystal city, you should get familiar with Metro as it will take you almost anywhere you want to go in the city, and is easy to use. Get yourself a Smartrip Card, an electronic farecard which you use to enter & exit the system.  They recently changed the card; it still costs $ 10 to buy, but that now includes $ 8 in fare, so the card only costs $ 2 net.  And since they charge a $1 surcharge on top of the fare for every trip you take using a paper farecard, it pays for itself in just one round trip, and then saves you a buck every time you use it.

Freddies is a gay bar not far from you in Crystal City - always worth the price of admission assuming you have an open mind!

http://www.washingtonian.com/packages/food-drink/the-100-very-best-restaurants-2012/ for an unbiased look at the best restaurants. You can also read the blog http://dc.eater.com/.

As for night life.. depends what your looking for... but DC is full of terrific bars/night clubs all within a 15 minute cab ride of you