Early in “Men, Women & Children,” the latest from director Jason Reitman, there is an overhead shot of people in a shopping mall, looking down at their cell phones. The image, one of the film’s most memorable, contains an implicit commentary, that modern people are like this and shouldn’t be, that their heads are stuck inside their machines. The picture, which opens Friday — and which opened the Mill Valley Film Festival Thursday night — tells a wide-ranging story following several families, most of whom have problems a lot bigger than the Internet, though the Internet helps make them worse. A teenage girl (Olivia Crocicchia) whose values are entirely distorted by false notions of glamor and stardom. [...] the movie shows adults (played by Dean Norris and Jennifer Garner) reacting to their children’s online lives in misguided and destructive ways. The movie isn’t prescribing or pointing fingers, but trying to capture the essence of how people are living now. There’s an image that’s repeated throughout “Men, Women & Children,” of the earth as a tiny blue ball, as photographed from billions of miles away. (In his recent movies, he has been better at drama than he ever was at comedy.) Rosemarie DeWitt is enigmatic as a wife and mother with a dark streak, and Judy Greer pursues an interesting line as a single mom who, one seemingly logical step at a time, makes a series of wrong choices.