Twins Justine and Perry have left their home in Australia and embarked on the road trip of a lifetime in the Pacific Northwest.    It's been a year since their dad lost his battle with cancer and Justine became the sole caregiver for her autistic brother, Perry. Now Perry has been accepted into an assisted-living residence in their hometown, Brisbane, Australia, but before he takes up residence, they're seeking to create the perfect memory.    For Perry, the trip is a gloriou