Prepare for major throat lumpage by the end of this buoyant coming-of-age tale, elevated to a glorious level by its extraordinary cast. Walter (Haley Joel Osment: A.I. Artificial Intelligence), 14 years old, neglected by his mother (Kyra Sedgwick), and adrift on the sea of directionless adolescence, is dumped for the summer with his crazy old great-uncles (Michael Caine: Austin Powers in Goldmember and Robert Duvall: Open Range) in rural Central Texas, with no phone and no TV for distraction. But the uncles tell marvelously entertaining tales of adventure and romance in exotic locales, dramatized by writer-director Tim McCanlies (The Iron Giant) with exhilarating B-movie glee. Unlikely as the yarns are, their veracity is beside the point — Walter is inspired, catching his uncles’ infectious lust for life and blossoming as a confident young man. Osment is that rarest of child stars, not merely a “performer,” a cute mimic in costume, but an actual actor — he has an inner fire that many actors twice his age cannot muster. Caine and Duvall, it almost goes without saying, are a delight in roles that delicately balance comedy and tragedy. This is a lovely and appropriately sentimental stew of old-fashioned values like honor, valor, love, and home. Bring Kleenex.