A Hopkinton mother was driving while on drugs with her children in the car Wednesday when she crashed into a parked car in Salem, according to police.Police said Sarah Breau, 29, told officers that she drove to Lawrence, Massachusetts, to buy heroin and was "nodding off" when she made a dangerous U-turn on Main Street, pulled into a parking lot and struck a car.Officers found Breau wandering away from her car when they arrived on the scene. They said she was noticeably impaired by narcotics.A subsequent search of Breau's car found several bags of a powdery substance and two children, ages 8 and 9, police said.Breau is charged with possession of a controlled drug, endangering the welfare of a child and criminal mischief.She was arraigned Thursday and later released on $5,000 bail.