We are hoping to get S/P/D early next year. We are first time WDW visitors. As a money saving measure we were planning to buy one park/day tix with an upgrade to park hoppers on site if we feel we're too restricted. But if we've paid the child price for the original tickets how will the upgrade be handled if we did it in the park? Would we be charged the adult rate? Would it be better to just buy park hoppers to begin with so we don't lose the discount?