If the girls need a break from D.C. and to do some shopping, take the metro to Pentagon City (Arlington, VA) -- there is a large, upscale mall at the Pentagon City metro stop. There are a lot of souvenir stands outside to buy t-shirts. Of course, in the mall, there are a lot of souvenirs available too. I lived next door to this mall for one year last year and this is a very safe area. Pentagon City (Fashion Centre at Pentagon City) mall is also a stop on the double decker bus tour.
Inside the mall, there's the usual food court. Grown ups can enjoy the Ritz Carlton lounge while the girls shop and eat ($5 sliders, $5 pizza.) There's also a full menu that you can order from in the lounge and there's a separate restaurant.
Here's a link to the list of restaurants in the food court (there's also a sit down restaurant but it's expensive):
http://www.simon.com/mall/malldirectory.aspx?id=157
Across the street from the Pentagon City mall is a California Grill (and a Starbucks both are on S. Hayes Street. I like the California Grill and it's large enough that it could handle a large group (call first though because it does get busy.)
A five minute walk from Pentagon City mall / metro stop is a restaurant row that has a lot of choices at 1201 S. Joyce Street. There is also a grocery store there.
A ten minute walk from Pentagon City mall / metro stop is another restaurant area on 23rd street. There are a couple of Italian restaurants, an American diner called Cesar's diner (open for breakfast), a Greek restaurant.
Here's a link to the Crystal City restaurants:
http://washingtondc.menupages.com/restaurants/all-areas/crystal-city/all-cuisines/
I also second the Verizon Center area like the other poster said for A LOT of restaurant choices besides a movie theater if you need a break from the heat or if it rains -- there's an upscale food area with restaurants and food kiosks (I remember a crepe place.) The shopping area is called Gallery Place. The metro stop for the Verizon Center is Gallery Place / Chinatown. I can't recommend any of the Chinatown restaurants even though I worked at this area (for Chinese food for an office lunch, we trekked across the city if that tells you anything.)
Here's a link about Gallery Place:
http://dc.about.com/od/shopping/a/GalleryPlace.htm
I ate at the Five Guys burgers restaurant at H Street NW and 9th Street NW many times and liked the burgers (I worked across the street from this restaurant.) You can't beat the price of a Five Guys burger -- even in Washington, D.C. (and the burgers are just really good too.) Be aware that Five Guys gives patrons peanuts as a free appetizer as soon as you walk in the restaurant in case anyone in your group has a peanut allergy.
Here's a link to the Five Guys:
http://maps.google.com/maps?hl=en&s...esult&ct=image&resnum=2&sqi=2&ved=0CCgQ_BIwAQ
Here's a link to the Verizon Center area restaurants.
http://dc.about.com/od/restaurants/a/RestNearVerizon.htm