Kenneth Feld, head of the Ringling Bros. and Barnum & Bailey circus headquartered here, was named "Headliner of the Year" by the Austin, Tex.-based Headliners club. Feld, who also presides over two Walt Disney ice extravaganzas and the Las Vegas spectacle "Beyond Belief," starring illusionists Siegfried & Roy, was toasted "for his dedication to safeguarding one of America's greatest institutions and for his achievement of maintaining the freshness and spontaneity of live entertainment in an age of prerecordings and canned laughter" . . .

Rock star Vanity, the former Prince girlfriend and prote'ge', showed up at Morton's in Georgetown for dinner Friday and admired the steak knives. Restaurant manager Michael Sternberg gave her a set, just as he did last year when Dustin Hoffman came in and admired the knives. It could get expensive if word gets around . . .

Former vice presidential candidate Geraldine Ferraro and her husband John Zaccaro renewed their wedding vows in a Roman Catholic ceremony yesterday at Our Lady of Mercy Church in Forest Hills, Queens, N.Y. The couple will observe their 25th wedding anniversary in July . . .

The new Sheraton Grand Hotel at the foot of Capitol Hill hosted a black-tie dance Friday as part of its grand opening. The Friday evening dance was a fundraiser for the Capital Children's Museum on its sixth anniversary and a special salute to Ann Lewin, the founder and executive director of the museum. Mayor Marion Barry was there to proclaim it Ann Lewin Day . . .

"Too Close for Comfort" star Ted Knight, this year's national chairman of the National Salute to Hospitalized Veterans, is to visit patients at the Washington Veterans Administration Medical Center tomorrow. Knight, who also played Ted Baxter on "The Mary Tyler Moore Show," is a decorated World War II combat veteran who spent time convalescing in a VA hospital after the war . . .

This may be veteran dancer-actor Donald O'Connor's year. He finished the filming last week in upstate New York of what is described as his dramatic feature film debut in "Miracle in a Manger," to be released this Christmas. Last month he was at the premiere of the film "That's Dancing!," in which he is featured. And coming to Broadway this year is the theatrical version of "Singin' in the Rain," O'Connor's most memorable film performance . . .

And as luck would have it, a Maine handyman looking for some quick cash to help heat his drafty home, picked up a paint-splattered canvas he had purchased in a flea market for $20 and found he owned a Jackson Pollock worth about $30,000. Philip Champagne contacted New York art dealers, from whom he knew he would get top dollar, but he was told it couldn't be sold until a July auction. "That's not good enough for me," he said. "You can't do art when you have to worry about heat and electricity."