December is going to be celebrity time in Washington, starting with the Kennedy Center Honors next weekend and carrying through with several major White House Christmas functions. Singer Andy Williams will be on hand to entertain at the Venezuelan state dinner Dec. 4, and on Dec. 10, weatherman Willard Scott and Mister Fred Rogers will be the stars of the Diplomatic Children's Party. The following night, society bandleader Lester Lanin will play at the Congressional Ball at the White House. Lanin has performed for presidents going back to Roosevelt and Truman; eight times while John F. Kennedy was in the White House; and twice for Lyndon B. Johnson. He also played at Tricia Nixon's pre-wedding reception at Blair House. On Dec. 20, Dom DeLuise will perform at the senior staff Christmas Party.

And actor Warren Beatty, who is expected for tomorrow's gala celebration of the 70th anniversary of The New Republic magazine at the National Portrait Gallery, is also expected to be back in town next week to emcee the Epilepsy Foundation of America dinner honoring Rep. Tony Coelho at the Hyatt Regency Capitol Hill. Cochaired by the political odd couple of Anne Wexler and Robert K. Gray, the $500-a-ticket, black-tie dinner is expected to raise $500,000 for the foundation. Coelho, who was kicked out of a Jesuit seminary when his epilepsy was discovered, is expected to be saluted by a list of colleagues, including former president Jimmy Carter, Sens. Edward M. Kennedy and Robert Dole, Reps. Geraldine Ferraro and Guy Vander Jagt and Speaker Tip O'Neill.