I live and work in DC. You do *not* want to drive in DC. Not only are the street lights on brown poles on the side walks (they don't hang over the road) but parking is a nightmare and rediculous ($25 per day), and most of street signs are really hard to read. If you want to go to one of the main memorials (Vietnam, WWII, Lincoln, Jefferson, etc), go to the Metro station by your hotel, buy a $5 (all day pass) and get off the metro at the "Smithsonian" station. That will put you on "The Mall". Most of the memorials are on The Mall. It's about a mile from one end to the other, but walkable. If you want to see the Whitehouse or Monument, call ahead. Tours book fast.
If you want to go see Arlington Cemetery or one of the memorials that is off the Mall then get a map and figure out the closest Metro station.
Be prepared to do a lot of walking. DC is mostly a walking city. oh, watch out for the traffic along Constitution and Independance. Speed limit is 30, but people go 40-50 if they can.