The American Film Institute Associates on Thursday announced that Walter, Carol and Charles Matthau will receive the first AFI Platinum Circle Award, a new trophy to honor a family of artists.The AFI Associates, a major support group of AFI, has raised more than $2.25 million for the org. The luncheon honoring the Matthaus will be held Sept. 18 at the Beverly Wilshire Hotel. Ann-Margret will present the award and serve as honorary co-chairwoman of the luncheon along with Sophia Loren and Goldie Hawn. The tribute will be produced by Fred de Cordova and AFIA member Carolyn Sargent. The announcement was made at a reception at Tiffany & Co. in Beverly Hills. Tiffany will create and donate the Platinum Circle Award that will be presented to the family. Walter Matthau has starred in 60 movies and 23 plays. His wife, Carol, authored her second book last year, “Among the Porcupines,” a bio about her early friendship with Truman Capote, her troubled marriage to William Saroyan and her successful second marriage to Walter. Their son, Charles, 32, is the director-producer of “The Grass Harp,” released last year. He previously directed “Doing Time on Planet Earth,” and the 1993 CBS vidpic “Mrs. Lambert Remembers Love,” which starred Ellen Burstyn. Chairwoman of the AFIA Platinum Circle Awards is Dolly Gillin. For ticket info, call (213) 856-7897. AFI Associates president Helene Tobias said the kudos is intended to be an annual event.