From Dulles Airport , you have the same options except there is no direct Metro service. From BWI Airport , you can take taxi or train service. Amtrak provides service to Union Station in downtown Washington. Washington offers great public transportation. Children 4 and under ride free.
Taxis are easy to come by in Washington.
There are also surcharges for extra passengers, fuel and rush hour commutes. Parking downtown is difficult. Parking meters are limited and you need to pay close attention to the posted signs or you may return to find your car has been towed from meters during rush hours. Just like any other major city, you'll need to take common-sense precautions against crime in Washington. Travel in well-lit areas at night, and don't walk alone.