Fairfax County police are offering a hands-on, learning adventure for parents and guardians of teenagers. Called “Hidden in Plain Sight,” it’ll be held Wednesday, July 20, from 6:30-8:45 p.m., at the Sully District Governmental Center, 4900 Stonecroft Blvd. in Chantilly. Attendees will be guided through a pre- sentation opening their eyes to what’s right in…