Our Disney vacation begins 4/26 where we have reservations at a Disney resort. However, we will be coming in the day before and were thinking about staying at a cheaper hotel outside of Disney the night before. Our idea is to stay at a hotel with an airport shuttle, take the airport shuttle to the hotel and back to the airport the next morning where we would catch the Magic Express to our resort. Would this work? Can we register for the Magic Express upon arrival at the airport or do we have to be preregistered to take it the day of our arrival?