There is plenty to see in Washington and if you are planning to come to the wedding here are some tips:
Some Washington sights and museums are more easily seen by arranging for advanced tickets.
Tickets for tours of the Capitol and the White House can be available through your congressman or senator. If your time is limited, the tour of the capitol provides somewhat more to see.
The Smithsonian is commonly wrongly referred to by visitors as a single museum. It is a collection of 19 government museums and the national zoo. While the Smithsonian has the advantage of being free and includes the Air and Space Museum, the National Museum of American History, the Portrait Gallery, the American Indian Museum and the new National Museum of African American History and Culture, several big museums are separate. Among them: The National Gallery. The tour of the Treasury’s Engraving and Printing facility where money is made is also separate and may be closed down for the wedding.
It’s generally pretty easy to get into the Smithsonian museums. The exception is African American museum, where you currently have to line up early in the morning for timed tickets later in the day and those too are hard to get. Details are here
If you are planning to go to the Holocaust Museum, you may be able to get timed tickets in advance for $1, though they may not be needed in September.
The Washington museum closest to the wedding hotels, the Phillips Collection, is relatively easy to go through in a short time and has one of the world’s most famous Renoir’s. The museum is undergoing some renovation and while some rooms may be closed, it says that the Renoir and its Rothko rooms will be open. The Phillips is a private museum and charges about $12 a person.
Washington also has a wide variety of walking, bus and boat tours. TripAdvisor recommends this site for more details.
The National Park Service offers a number of walking tours. Hop-on, hop off tours are offered by several companies including BigBus, whose yellow route stops outside the Hilton, whose site has more about it. (Note that if you take it, you have to transfer to the red line to see the museums on the National Mall). There are boat trips along the Potomac leaving from Georgetown including this one. There are also more tour choices leaving from Union Station (which is a ways away from the hotels, but accessible on Metro.)