It was a one-mile walk home from a Silver Spring park on Georgia Avenue on a Saturday afternoon. But what the parents saw as a moment of independence for their 10-year-old son and 6-year-old daughter, they say authorities viewed much differently. Danielle and Alexander Meitiv say they are being investigated for neglect for the Dec. 20 trek — in a case they say reflects a clash of ideas about how safe the world is and whether parents are free to make their own choices about raising their children. “We wouldn’t have let them do it if we didn’t think they...