David Geffen was feted by 66 VIPs including Steve Martin, Lorne Michaels, Ron Meyer, Candice Bergen, Graydon Carter and Jann Wenner on Monday after a debut of Susan Lacy’s “American Masters” doc on the mogul. “How do you follow Mike Nichols,” mused Barry Diller in a line of power players making toasts at La Grenouille. Diller said when his wife Diane von Furstenberg gets sick, he brings her medicine but Geffen “brings her information.” An LA screening’s being hosted Tuesday by Tom Hanks, Warren Beatty, Annette Bening, Steven Spielberg, Jeffrey Katzenberg, Robbie Robertson and Cher. “Even if no one else shows, it will be gridlock on the red carpet,” quipped a spy.