Just remember, July is PEAK season in DC and the Smithsonians are packed, packed, packed. The Smithsonian map booklet has all the museums in it with all the exhibits, etc. Decide ahead of time (like Disney) which museums you want to see most, prioritize them in order of which ones you want to see, and then what exhibits you want to see in order within each museum. Air and Space, Natural History are still relatively easy to navigate in the crowds. American History backs up at certain exhibits (like First Ladies' Ballgowns) and can have waits up to an hour to go through the exhibits. Decide which ones you really want to wait for and which can be skipped.
Same lines/waits apply to the National Archives.
Others like already mentioned, have timed tix.
I highly recommend The Holocaust Museum for older kids (SC Minnie, it would be perfect for your DD15 since she's studied it, it is very sad, but very powerful and educational.)
Even when requests are put in to state representatives, White House tickets are very hard to get, so have alternate plans ready, just in case.
Arlington National Cemetery is a great tour, as well as we enjoy Georgetown. Georgetown is a great little break away from the history and has some great shopping and great restaurants.
The Basilica of the Shrine of the Immaculate Conception is a must see if you are Catholic or love church history and art. There are scores of little shrines there that one is more breathtaking than the next.
The night tours are amazing but yes, can get expensive. If you want to do it on your own, we like walking (usually close enough to...) to the WWII Memorial, spectacular at night and then walk up to the Washington Monument and from there you can see many of them, it is a great middle point to enjoy the night.
Some of our favorite restaurants are:
Five Guys Burgers
Hard Rock Cafe
M&S Grill (seafood)
Cafe du Parc (at the Williard hotel, this for brunch buffet, wonderful!)
Gordon Biersch
Old Ebbitt Grill
Clyde's Chinatown
Martin's Tavern (Georgetown, where JFK proposed to Jackie)
Old Glory (Georgetown)
yes, they are toursity, but hey, we like to be tourists when we're there!
For lunch we usually hit the Sabrett hot dog carts, or pack our own lunches. It leaves some more cash for a nice, relaxing dinner.
In July, be prepared for tons of walking and hot weather, so make sure you hydrate with lots of water. There are ususally lots of vendors selling cold waters all over the place for $1 per bottle which is reasonable and better than lugging lots of bottles around with you all day. My kids love the fan spray bottles from
Walmart to carry with them, and definately use them!
Also for kids at the National Parks, which all the monuments are a part of, you can buy a little passport and get all the places you visit stamped. It's fun and the Park Rangers ususally engage with the kids. In places like the White House Visitors Center, kids can do some activities in a little workbook they give you and earn a Park Ranger certificate and badge. That is all free except for the little passport which is a few dollars. A great way to learn and a great souvenir for the kids too.
Have fun to all who are going!
We will be there in July as well. We go every year with DH's company, they hold meetings each year there that they invite the family to attend.
we'll be there 3 or 4 days.
$49.99 a person! 
you can pick my jaw off the floor now!
