Superwealthy businessman Meshulam Riklis has no problem with having a wife who is 30 years younger than him, if his wife is ever aspiring actress/singer Pia Zadora. Riklis, who was in town for his wife's Kennedy Center concert Sunday, told a story of how he and the 28-year-old Pia were on vacation and riding in an elevator with another woman. Zadora was wearing a small bikini. According to Riklis, 58, the woman turned to him and pointed out that he shouldn't allow his granddaughter to get so much sun. He roared with laughter at his story.

Zadora was here as part of a national tour. She had performed Saturday in Boston and Friday night at Carnegie Hall in New York. Not bad for someone who has one record under her belt. Unfortunately, Zadora sounds better on her record than she did at the Kennedy Center. She has a big voice, but her stage presence and performance are wooden. Even backed by a 40-piece orchestra and, as she said Frank Sinatra advised, singing the standards didn't help.

At a buffet supper after the concert in the Kennedy Center atrium, Riklis and Zadora made the rounds at each table, where the guests included Sens. John Warner, Chic Hecht and Dave Durenberger; Reps. Norman Lent and Bill Lowery; Republican National Committee Chairman Frank Fahrenkopf; former ambassador Alejandro Orfila; Chief of Protocol Selwa Roosevelt; and media personalities Glenn Brenner, Susan King, John McLaughlin and Bill Plante. End NotesWashington Ballet artistic director Mary Day and her executive director Elvi Moore flew down to Miami Saturday to watch a former student dance Act II from "Swan Lake" with Mikhail Baryshnikov. The young dancer, Bonnie Moore, is not a principal with the American Ballet Theater, but Baryshnikov still selected her from the corps de ballet to dance with him, and when the dance ended, she received an unexpected standing ovation. She'll be with the ABT when it comes here next month, though it isn't known if she will dance a principal role. Day says she expects Moore to become one of ballet's greats . . .

Syndicated columnist Art Buchwald and endcol playwright Sam Shepard were among eight elected to the prestigious 250-member American Academy and Institute of Arts and Letters, which honors men and women of distinguished achievement in literature and the arts. Pulitzer Prize-winning humorist Buchwald is only the fourth humorist to be elected. The others are Mark Twain, Peter De Vries and Russell Baker. The other new members are composer Morton Gould, painter William Bailey, sculptor Varujan Boghosian, sculptor Mark Di Suvero, painter Wayne Thiebaud and historian Donald Keene . . .

Socialite Claus von Bu low, who was acquitted of attempting to murder his wife Sunny, has asked a judge to dismiss a $56 million civil suit filed against him by his two stepchildren, Annie-Laurie Kneissl and Alexander von Auersperg. He contends in his legal action that the stepchildren have no right to sue because a court-appointed committee has been handling his wife's financial affairs since she lapsed into an irreversible coma in1979 . . .

Former President Nixon speech writer Bruce Hershensen, who is a chief contender in the California primary to oppose Sen. Alan Cranston in the upcoming California senatorial race, was in town over the weekend for a dinner party at the home of former Nixon administrator Dick Moore, hosted by Moore and Angela Bay Buchanan. The dinner brought out a powerful group of supporters, including Vice President George Bush and his wife Barbara; former senator Jim Buckley; former attorney general John Mitchell; Reagan aide Pat Buchanan; speechwriter Tony Dolan; former Reagan aide Lyn Nofziger; columnist Bob Novak, and television personality John McLaughlin and his wife Anne . . .

Hollywood is not happy about the upcoming movie on the life and death of comedian John Belushi. Clearly, one of the toughest things will be in casting a credible actor to play the troubled, brilliant comic. The movie of the book "Wired: The Short Times and Fast Life of John Belushi" by Washington Post Assistant Managing Editor Bob Woodward is closer to reality now that Mike Fenton has been hired as casting director. The highly respected Fenton has cast such movies as "E.T.," "Raiders of the Lost Ark" and "Back to the Future." The producer of "Wired" is Ed Feldman, who produced Oscar contender "Witness" . . .