I've been looking around the DC area because we may be moving but I don't live there and can't offer any real help.
What I did come across in my searches was an AP group in DC. Maybe a Google search would give some results. Also, Craigslist had lots of offers for childcare but I certainly can't recommend one.
I might also consider an established school that accepts younger kids ~ something like a charter pre-K, a Waldorf, Montessori or something like this. Oh, and also Uni. child care centers can sometimes be really good. When checking into schools, it looks like pre-K in this area starts pretty young.
Good luck and I hope you have a pleasant move.
You're also welcome to post this question on my tread about DC for families. There are a few locals posting there.
ICM~ Great idea aboutthe Uni childcares. They are GOOD. The people who work there are working on their degrees in Early Childhood Education, and unlike MANY childcare workers actualyl apply what they are learning/have been tuaght. They have knowledge of child development and are generally kind and very loving. Check out American University or GW, although it may be a bit out of your way, and traffic would suck in the a.m. My mom loved American University. She stayed there when she first moved to DC while looking for a job in the summer months when many students went home (she stayed in the dorms)