We are going doing the 2 week of July and we found excellent rates on groupon. 3 days at the Arlington Clarion for $360, breakfast included. Parking in DC will be by Panda parking, groupon had a great deal with them, $12 for any thing up to $25. The price for taking the train for 4 people will be more than the $12 so this is why I chose to go this route.

Another vote for Udvar Hazy. It's Smithsonian's second, lesser known air and space museum~without the crowds.

One of the things my teenager enjoyed in DC was the Museum of Crime and Punishment and the interactive exhibits.

Hope you have a wonderful visit to DC - it's such a great place to visit and take kids also. You have received many great tips here and the good thing about DC is most everything is free so great for a budget.

The metro is easy to navigate also. Another thing you can think about for getting about DC is to download free iphone tours. Here's a website I found, not sure what type phone you have.

http://www.top10travelapps.com/search/washington%20dc

My daughter, SIL and 2 grandsons (now 16 & 13) went to DC last April and they loved it. My daughter is a teacher so well planned their itinerary. They had a tour of the Capitol Building and they found that interesting. Did all the monuments as well. I asked my youngest grandson what he liked best and he said visiting Arlington Cemetery and Changing of Guard (I believe the ceremony is every 1/2 hr. in summer). Do try and get to see that. There is a tram tour you could take.

http://dc.about.com/od/monuments/p/ArlingCemetery.htm

Good luck and have fun. Remember your sunscreen, water, and hats! LOL

Lots of walking too.
You can take the metro right to the

Sorry, disregard the last line, had it posted and couldn't delete it. What I was going to say is that you can take the metro to Arlington Cemetery stop and it's a short walk to visitor's center to purchase tickets.

Someone may have mentioned this but check your Congressional representatives websites. They can often get you tickets for tours. Our Senator hosts a free breakfast where we got to meet her and then get a free tour of the Senate by one of her staff. We took a little train from her office building to the Capitol building and exchanged seats with John Kerry (this was a few years ago.) We were also able to obtain tickets to see the Senate and House of Representatives in session. -- very cool.