“This is my first day off in weeks,” Dave Grohl says, barefoot in his kitchen in jeans and a biker T-shirt, big goofy Dave Grohl grin on his face. The 48-year-old Foo Fighters frontman doesn’t get much downtime these days, between making records, touring, directing documentaries and gigging with pretty much anyone who asks. (Grohl: “I just like to jam!”) But today, he finds himself uncharacteristically unoccupied. “What should we do?”
Grohl already dropped his two older daughters off at special-effects camp. His youngest, three-year-old Ophelia, is at pre-school, so now he has the day to himself. Next week, the Foos will hit the road in support of their ninth album, Concrete and Gold, flying first to Chicago, then Southeast Asia, Australia and Europe, then back home to throw their…