Reared first in England and then in New York City by parents from opposite sides of the Atlantic, Don Thompson remembers sailing aboard the Queen Mary and other great ocean liners as a child. In more recent years, he and wife Sally have taken more than a dozen cruises. So no wonder “Charley’s Cruise,” the flagship, so to speak, of Thompson’s first trilogy of mystery novels, takes place aboard a cruise ship doodling around in the Caribbean.