Hello there John!
Welcome to planDisney. We're so glad you stopped by with a question today and I'm excited to hear you have a visit to 
Walt Disney World Resort later this year. I'd be happy to help!
I'm sorry to hear one of your travel partners won't be able to join you for your upcoming visit. It's never fun when vacation plans have to change, but unfortunately, things do pop up. I'm not sure whether you've purchased your tickets through a third-party provider or directly through the 
Walt Disney Travel Company. If you've used a third party I would reach out to them to confirm the terms and conditions on ticket modifications. 
If you purchased directly through Disney or have already linked your tickets to your 
My Disney Experience account, you can contact a Cast Member for assistance. The 
value of a wholly unused, expired ticket can be applied toward purchasing new tickets of equal or greater value, so you should be able to apply that value to a future visit. You can reach out to the 
Ticket Help Desk by phone for assistance in adjusting the dates and further details. You can also stop by the ticket window at the main entrance of each park or visit 
Guest Relations in person during your upcoming visit.
Be sure to experience 
EPCOT International Festival of the Holidays and take time to enjoy the beautiful holiday decor in the resorts. Last year, I loved the 
life-size gingerbread house at 
Disney's Grand Floridian Resort & Spa and the incredible gingerbread carousel at Disney's Beach Club Resort. So impressive and so deliciously scented, too!
John, I hope this was helpful. If we can offer any additional planning assistance please reach back out to us.
Magic and memories,
Amy