Dc
Both lenses IS the best option
As for tripods...
I was there this past spring for a week, and EVERY time I tried to use a tripod I was hassled or strong armed.
Locations I was unable to use a tripod:
-Both sides of whitehouse
-Lincoln Memorial
-Capital Building
-WWII Memorial
Then I gave up trying. I was told a variety of things from a variety of "law-enforcement" officers (DC has like 4 different law-enforcement agencies roaming). It seems the prevalent excuse was "impeding the flow of foot traffic".
At one point, in front of the white house around dusk, I had my tripod set up with my tele peering between the bars of the gates. Some goon approaches me and says I have to take it down. I ask why, and he says that it is a hazard for pedestrians. I say ok, is the street ok then? He tells me its fine. I take a few steps back, and set down in the street. 2 minutes later, 3 PD officers rush me and freak out. I tell them that "that guy(pointing)" said I was clear. They were not pleased with me OR him.
My personal favorite though: At the WWII memorial, my dad (an army vet) and I were checking it out, its beautiful, and I wanted to take some night shots. After about 3 exposures, a National Park service lady approaches me and tells me to take it down. I ask why, and she says "Out of respect for the fallen" so me, getting mad now (I just wanted some night shots from DC!!!) ask her "Well what about all those giggling girls using their flash camera posing in front of the monument?" And she responds "Sorry, regulation".
That is why I made my claim. I was unable to fire off more than 10 shots total from the tripod during my entire stay in DC.
PS: Look into renting a lens!!!
I brought a 10-22mm, an 18-55 non IS, and a 70-200 f/4, and still did not have the "right" lens.
Look into a f/2.8 lens, or better yet, a 2.8IS.
You will probably spend time in museums. Museums are dark+No tripods allowed in museums=Bad.
I now have a 17-55 f/2.8 IS, and I WISH I would have had it in DC.