Pediatrician Dr. Tiffany Munzer has encouraging words for parents hoping to strike a healthy balance with summer screen time for their kids and teens. "There are things that they can do, even though the deck really feels sometimes stacked against them," says Munzer.Munzer, who is also a digital media researcher at the University of Michigan, has no illusions about the challenges parents face over the summer. Fulfilling, screen-free activities ar…