When American Ballet Theatre artistic director Mikhail Baryshnikov dances for President Reagan and his wife Nancy at Saturday night's inaugural gala at the Convention Center, he will not be performing to recorded music. It will be Frank Sinatra himself singing "One for My Baby" at the side of the stage . . .

Julie Christie and Ann-Margret are to be at the K-B Fine Arts Theatre tonight for the benefit premiere of "The Return of the Soldier." The film also stars Glenda Jackson and Alan Bates. The showing and Regent Hotel reception that follows will benefit Women Make Movies IV, the Fourth International Women's Film for the Performing Arts . . .

Merrie Spaeth, the former director of media relations at the White House, has been named one of Glamour magazine's Ten Outstanding Young Working Women of 1985. Spaeth was recently appointed vice president and director of public relations for RepublicBank, Dallas . . .

It isn't enough that the city is filled with official inaugural activities. There are a President Ronald and Nancy Reagan for those who didn't get invited to the real thing. A Ron Smith Celebrity Look-Alike President and Nancy Reagan were at a swearing-in of sorts at Champions in Georgetown yesterday followed by an Inaugural Ball there last evening for all those whose other inaugural invitations were lost in the mail . . .

Helena Shultz, wife of Secretary of State George Shultz, was in fair condition at Georgetown University Hospital last night. Hospital officials declined comment on her ailment . . .

Now that he's leaving office, Delaware Gov. Pierre S. du Pont IV has revealed that he paints. The large painting hanging behind the two-term governor's desk titled "Ledbetter's Cottage" by D.A. Christmas (done at Christmas) was painted by the governor . . .