When Gao Huasheng, a university professor from Shanghai, began planning a two-week family holiday to San Francisco earlier this year, he worried about exposing his children to scenes of drug use or even gun violence.But in the end, the 44-year-old decided to go ahead with the trip – and his fears turned out to be misplaced. The family’s visit to the Six Flags Discovery Kingdom amusement park and road trip down the Pacific coast went off without a hitch.“My children said it was exciting, not...