Changing tickets when we get there?

[O'MalleytheAlleyCat]

We leave in less than 3 weeks for our trip. Right now, my son has a 10 day non-expiring ticket with 8 days remaining. It's that ticket that is linked to our reservation and was used when we picked our fastpasses. We recently decided to add another Disney trip in May and because of the number of days between the two trips, we will likely be purchasing an annual pass for my son when we get to Disney in October. I'm going to assume that guest relations can take of selling the ticket, linking it to our current reservation and also transferring the fast passes to the new ticket? Does anyone have experience with this? My son will be arriving early in the day and we won't get there until very late in the day, so he will probably be purchasing the ticket so he can have a little park time that day. I just want to be sure that the correct ticket is linked to his magic band when he enters the park and that his and our fastpasses won't be affected by the new ticket.

[DizneyRox]

Fast passes are tied to MDE not the ticket.

When he purchases that AP, make sure he tells then that he wants the new AP to be his active ticket, not the 10 day ticket. Otherwise it could use days from that ticket instead of the AP.