I have a trip planned for this fall and have tickets already. My father has decided he wants to join us but there is a risk that last minute he would not be able to go. If I get him tickets now and he does not join us, how do I go about using that ticket towards a future ticket purchase. Our next trip will be 2020, so they will expire by then. Is it something that needs to be done at the parks or can it be done online or over the phone so I can still make fast pass plans?