Right on schedule, the cyclists come back to the Ellipse for the National Capital Open Bicycle Races, Sunday from 10 to 4. Some of America's best and many from abroad will race from 16th and Consititution, back to the same spot, including a 31-mile men's National Prestige Classic that starts at 2:30.

And, on the C&O Canal, the mule-drawn Canal Clipper returns, with barge rides with costumed guides at 10:30, 1 and 3, Friday through Sunday, leaving from Great Falls Tavern in Potomac. Tickets must be purchased two hours in advance ($3; $1 for those under 12 or over 62). Call 299-2026.

Meanwhile, "The Greatest Show on Earth," Ringling Brothers and Barnum & Bailey Circus, will be filling D.C. Armory with clowns, tigers, acrobats, unicyclists, performing bears and who knows what-all, through April 27. Tickets are $5.50, $7 and $8.50. For information call 544-1620.

The Paul Hill Chorale will sing Beethoven's "Missa Solemnis," to the accompaniment of the Kennedy Center Orchestra with guest conducter Roger Wagner, in the concert hall Sunday at 3. Tickets are $4 to $10.50. Details: 254-3776.

Ever been to an Easter-Passover "Festival of Delights"? Well, Sunday (2 to 4) is your big chance, the Wakefield Recreation Center (8100 Braddock Road, Annadale) is the place, 25 cents is the price and bluegrass music and israeli folk dancing are chief attractions. For details call 321-7080.

Monday, 10 to 2, the White House grounds will be crawling with kids (eight and under, accompanied by an adult) hunting the traditional hardboiled and colored Easter eggs plus those signed by President and Mrs. Reagan, members of Congress and such celebrities as Charlton Heston and Burt Reynolds. Enter through the southeast gate. Call 456-7041.