What are some suggestions for a romantic date day and night in Washington DC?

I already have restaurant reservations, but I'm looking for things to do... This is a VERY special person and unfortunately I'm not from the area.What are some suggestions for a romantic date day and night in Washington DC?
Everyone is advocating the mall and tidal basin, but under full sun, you might get a little warm/sweaty out paddling around depending on the temperature. In the Spring, that would be great, but lately, anywhere between 78 - 95 degrees.



When it is not too crowded, the US Botanic Garden (free) at 100 Maryland Ave SW (Federal Center SW or Capital South metro stations) is usually quite beautiful inside and the US Post Office (free) Tower has a great view esp in the evenings at 1200 Penn Ave (Federal Triangle Metro). These are lesser known spots and thus less crowded by tourists.
Walk around the mall, see the museums, there is a carosel outside the museums, how romantic is that.What are some suggestions for a romantic date day and night in Washington DC?
Go to a few of the museams for the day (try the Natural History museam and an art museam) There is also a sculpture garden which i hear is really beauitful. Go to dinner, then walk around the monuments at night.
I would recommend paddle boating in the tidal basin, its not expensive, easy to do and you get a good look at the monuments etc. After dinner I would recommend you go to Georgetown and walk up the main street. There is a place called cafe Leopold's that has great coffee/after dinner drinks/cakes http://kafeleopolds.com/. Its like behind the street and threes little tables etc. its a great place to sit and relax. You can also go down the the Georgetown waterfront.





My other suggestion is to take a Potomac dinner cruise. Its awesome to sit in the huge boat and enjoy a good dinner (done that once).