In case you were wondering why you have Monday off from work - and it's easy to see how you might forget - it's in honor of George Washington's birthday. Take some time off from bargain-hunting to celebrate more traditionally.

Sunday, at Great Falls Park, Va., the National Park Service will have special films, colonial music and children's activities from 10 to 2. Details: 759-2925.

The District's official observance is Monday morning at 11, with a wreath-laying at (surprise) the Washington monument.

Alexandrians, meanwhile, have been at it all month long. They don't fool around when it comes to celebrating the birthday of their most famous citizen, and this weekend you can choose from: Strolling minstrels singing in Old Town shops and sidewalks on Saturday; a Birthnight Ball ("dress is colonial or black tie") Saturday night at 9 at Gadsby's Tavern (549-0205 for details); free tours of a naval ship docked at one of Alexandria's piers on the Potomac, Saturday through Monday; a reenactment of a day in the life of a Revolutionary War camp by the First Virginia Regiment of the Continental Line Sunday, 11 to 4 at Fort Ward Park, 4301 W. Braddock Rd. Wrapping it all up, the annual parade will wend its way through Old Town streets Monday from 2 to 4. More than 80 units will participate, and there'll be appearances by George and Martha themselves - or reasonable fasimiles thereof.