On a recent Saturday, at Bob’s Steak & Chop House at the Omni Berkshire Place, on East Fifty-second Street, Shaun Cassidy, the sixty-year-old performer, writer, and producer, ordered an Arnold Palmer “with more Arnold than Palmer.” He wore a crisp slate-blue suit, a pocket square, and a white shirt with the top buttons undone—a genteel update of his late-seventies look, when, as a teen heartthrob, he appeared on a popular poster wearing a revealing satin jacket. Beside him was a box of 3-D slides taken by his grandfather at the 1955 movie première of Rodgers and Hammerstein’s “Oklahoma!,” which stars Cassidy’s mother, Shirley Jones. Jones, then twenty-one, had ridden to the première with her parents, in a surrey with a fringe on top; on Saturday, at age eighty-five, she would…
