My family is planning on heading to WDW next year. On a strictly numbers basis it makes sense for me to buy an WDW AP for the hotel, food and merchandise discounts. However, I would like to convert it to a Premier if I can swing a Disneyland trip later that year. What does it take I make the switch when I get to Disneyland? I am holdin off doing the Premier outright on the chance I can't get to DL but want to have te option later.