The premiere of Barbra Streisand's new Movie "Funny Lady" is the occasion for a charity benefit for the Special Olympics for retarded children. Dick Cavett, the scheduled host, is expected to interview arriving guests including at press time First Lady Betty Ford and to introduce a montage of clips from Barbra's films. The highlight of the show is Barbra's first live television concert, a 20-minute segment. The program is telecast from the John F. Kennedy Center for the Performing Arts in Washington D.C.