We finally used our old non-expiring tickets that we purchased in 2017. I wanted to share my experience with anyone else who may still have those kicking around.
I went to the ticket office at Disney Springs to have the tickets activated when we arrived at Disney. I had used place holder tickets to make my park reservations before we left.
We had two adult and 2 kid tickets. One kid has since aged out. At first they were going to charge me to upgrade the kid's ticket to an adult one, but didn't in the end (I'm not sure why, but the supervisor said not to do that - I guess it's complicated on their end).
The tickets were activated and attached to
MDE no problem. BUT, they left the placeholder tickets with our reservations as well. There was some debate as to whether they should be removed, but they decided not to.
When we went to our first park the next day, this caused issues as the system was picking up the place holder tickets instead of the actual tickets. I had to go to guest services to get it sorted out. Basically, she deleted all of our place holder tickets and park reservations and then rebooked the park reservations under our actual tickets. It took a few minutes and messed up our EE RD plans, but she gave us a LL for Everest, so it was all fine in the end.
I hope this helps someone out there!