For a little while, it looks like "Up," Pixar’s 10th feature-length film, is going to be a downer. Not that there’s anything wrong with an animated film tugging at our tear ducts. But you can sense unease rippling through the younger halves of the family audience when, about five minutes into a spunky prologue, intrepid pre-pubescents Carl and Ellie abruptly morph into newlyweds, and then not-so-newlyweds.
