This may be one party that Washington's social lions won't be clamoring to attend. Martin Sheen, Cicely Tyson and 11 other actors come into town this weekend for next week's shooting here of the television movie now titled, "Race Against Winter." And hunger/homeless activist Mitch Snyder, a man who could have made millions with his instinctive ability to attract media attention, is hosting a preshooting cast party at his embattled shelter at Second and D streets NW.

On Sunday afternoon, the homeless are to meet Hollywood at the cast party that Sheen and Tyson have promised to attend with other members of Chuck Fries Entertainment Inc. and CBS Entertainment. The party, with cake, punch and hors d'oeuvres, will be held in Snyder's Community for Creative Non-Violence shelter in the former soup kitchen in the building's cavernous basement. Snyder is leaving no stone unturned; in addition to his homeless residents and the movie makers, he has invited House Speaker Tip O'Neill, Mayor Marion Barry, Sens. Mark Andrews and Arlen Specter, and Reps. Henry Gonzalez, Michael Barnes and Ted Weiss.

All the exterior shooting, mostly around the usual monuments and the District Building and Union Station, is to be completed next week with Sheen playing Snyder and Tyson portraying an elderly street woman who, the last time Snyder saw her, had a bus ticket in hand and said she was going home. Snyder said he hopes she arrived there and is still alive, but he has no way of knowing. All the interior filming for the movie, which is expected to air next winter, will be shot on the West Coast. A number of the street people will be used in the movie and paid for their services. The Snub for 'Murrow'

Tickets are reportedly moving slowly for the benefit showing of the Home Box Office movie "Murrow," the film that television heavyweights Dan Rather and Walter Cronkite oppose. Cronkite said "Murrow" is "a dull movie" and "a docudrama of the worst type." Cronkite and Rather both raised objections to tomorrow's screening of the film about CBS News founding father Edward R. Murrow to benefit the Reporters Committee for Freedom of the Press.

Their objections apparently were not with the film's portrayal of Murrow, played by Daniel J. Travanti, but with the way some CBS executives from that period -- William Paley, CBS founder and former chairman, and Frank Stanton, former CBS Inc. president -- are portrayed. There is a noticeable absence of anyone from CBS among those scheduled to attend tomorrow's screening of the film and symposium. The symposium panel, chaired by Hodding Carter III of "Capitol Journal," will include Edwin Diamond of New York magazine, Ed Fouhy, executive producer of "American Almanac," and Barbara Matusow of the Washington Journalism Review. End Notes

The American Historical Association's 1985 Book Awards from the Washington area include: Pete Daniel of the National Museum of American History for his work on the transformation of agriculture in the South; Joseph P. Reidy of Howard University and Ira Berlin and Leslie S. Rowland, both of the University of Maryland, for their editing of historical sources on emancipation; and Claire G. Moses of the University of Maryland for a book on 19th-century French feminism . . .

Political activist Robert McCandless, who was Hubert Humphrey's executive director during the 1968 presidential campaign, was married on New Year's Day to Marie Figueroa, who is on his consulting firm staff. The couple was married at his farm in Stanardsville, Va. . . .

Colleen Dewhurst and Paul Winfield, who are appearing in the Peter Sellars production of "A Seagull" at the Kennedy Center, are to be at the Duke Ellington School of the Arts this afternoon for a session with students . . .

At last night's press conference, President Reagan decided to break with tradition by calling on veteran Washington newswoman Sarah McClendon for the first question. McClendon, who recently underwent hip surgery, was back on the job for the first time since her operation and the president, who had telephoned her over the Christmas holidays when she was in the hospital, wanted to do something special for her. Traditionally the first question is asked by a member of the wire services . . .