The trailers playing ahead of the Pirates of the Caribbean: On Stranger Tides offer an inkling of who this franchise's main audience now is: Zookeeper, Mr. Popper’s Penguins and The Muppets. Given the adventure, the tension and the boldness of the rum-drinking, shaggy-haired Captain Jack Sparrow, one would assume the high jinks of this growing series would take the higher ground of kid-friendly fare. That would be wrong. Of all four installments in the franchise, this is certainly the most subdued and benign. Despite some bawdy humor between Johnny Depp and Penelope Cruz, “On Stranger Tides” is child’s play.