Depending on what format you're shooting, and how much you need to process, I MIGHT be able to lend the use of my darkroom. My darkroom is pretty small, but I've got sink space to be able to process up to 11x14 film in trays (6 foot sink). 8x10 in deep tanks, Jobo, or trays is very easy.
Hotels - the aforementioned options in Crystal City and Rosslyn are probably better bets. A friend of mine once got a fantastic deal at the Swissotel in the Watergate through Priceline. If budget is no object, there's always the Mandarin Oriental, which is a reasonable jaunt from the Jefferson and the WWII. Also, depending on schedule, I'd be willing to help out with logistics. One definite tip for shooting the WW II with a ULF - get down there before sunrise, because by 9 am the place is a zoo. Get it with nice low-angle cross-lighting, because as the sun gets up, the main plaza is totally exposed, and is washed out with glaring direct sun.