The music of The Beatles, and of John Lennon and Yoko Ono, is timeless. And yet, musician, songwriter and producer Sean Lennon says he feels a responsibility to promote his parents' legacy, by reminding the world of its power. He talks with Anthony Mason about the Oscar-winning animated short inspired by their anti-war anthem "Happy Xmas (War Is Over)"; the new HBO documentary "One to One: John & Yoko"; and about the "gift" of producing a new album of John & Yoko's music. | CBS Sunday Morning