Lovely weekend in DC. The many Cherry Blossom boat tours are a great way to spend a few hours on the water and to enjoy good weather. In Georgetown they have several companies offering boat tours. The good thing is that these are not expensive and a good way to spend a few hours if you are in the National's Capital.
*If you are traveling via Metro be sure to check wmta.com to check for delays before you head out. Also, Cherry Blossom festival is one of the most busy times for the metro system and there are long lines every where. If you can, travel early, bring lots of water and snacks with you, and buy your metro ticket as an all ticket to save time and money.