A week isn't enough time for the museums. They are almost all lined up on both sides of the Mall. Congress is on one end, Washington and Jefferson on the other, Lincoln a little further. The Zoo is up the Red Line a little North.

You might want to see the Tomb of the Unknown Soldier, that's in Arlington, across the Potomac river. There are tour busses, but you can walk most of it.

Consider staying at a hotel in Maryland or Virginia and riding the Metro downtown, it'll save you serious coin. It gets quite hot in summer, consider coming in April, May, September or early October.

https://www.wmata.com/