As the popularity of electric-powered bikes rises, Marin County officials are warning of increased accidents, especially among youth, and encouraging families to choose safer options if they are purchasing an e-bike for the holidays. New data released earlier this month showed that e-bikes made up a quarter of all bike-related 911 calls since early October, when the county began to distinguish the two. Forty percent of those accidents involved youth ages 10 to 19, while…