In December I'm taking my elderly mother and elderly Aunt on a Disney Cruise. However before the cruise we are staying for 2 nights at the Boardwalk Villas and will have one full day to do a park. As my aunt has never been to DisneyWorld I thought it would be a crime not to visit at least one park. And as most people think of the MK when they think of Disney I was going to take her to that park. Here is my question. If for some reason we don't go to the MK, will I be able to upgrade those unused tickets at a later day to a 4 or 5 day pass for the next visit and pay the difference? The one day tickets will be purchased from UCT.