Rory Kennedy never expected to get her mother Ethel’s blessing to make a documentary that would include her first interview in more than 30 years. “I called [my mom] up and said, ‘I am sure you don’t want to do this,’ and she said, ‘Yes,’ ” the director said Saturday when the doc debuted at the Nantucket Film Festival a ferry ride from the Kennedy compound in Hyannis Port. But Kennedy added that Ethel, 84, widow of murdered former Sen. Robert F. Kennedy, still wasn’t crazy about the title. “She doesn’t like her name, and I called the film ‘Ethel’ . . . Every time I say the name of the film she cringes,” Kennedy said. A cadre of Kennedys were spotted at the screening at the Dreamland Theater, including Robert F. Kennedy Jr.’s daughter Kathleen “Kick” Kennedy, who stars in HBO’s “The Newsroom.” Also at the festival, Diane Keaton presented “Something’s Gotta Give” director Nancy Meyers with a tribute. Amid the Nantucket summer set, Keaton was seen wearing “a black tux, black platform shoes and an ‘Annie Hall’ hat, while everyone else was practically nude,” a spy said. Meyers said she has plans to direct the first film that she hasn’t written, “The Chelsea,” by her daughter Hallie Meyers-Shyer. But first, she’ll direct Tina Fey in “The Intern.” The festival’s annual All-Star Comedy Roundtable featured Ben Stiller, Chris Rock and Jim Carrey and was moderated by “Saturday Night Live” star Bill Hader. The event will be aired on cable network Epix. News anchors Brian Williams and Chris Matthews also did moderator duty over the weekend. Williams brought daughter Allison, who stars in HBO’s “Girls,” along for the trip with his family.