Hi Robert, and welcome to planDisney!
I see nothing wrong with making any changes to your plans if necessary. The good news is that changes can be made, and that makes it convenient, especially when it comes to a
Walt Disney World Resort vacation.
If you purchase your 4-day theme parks tickets and choose to add a day later, you can make those changes as long as they are made prior to midnight ET the day before your ticket’s first use date. To add the additional days to a ticket, you can use the
My Disney Experience mobile app. Using the app, select the three lines at the bottom right and select “Tickets & Passes,” and then select “Change Ticket” and proceed through the process to add an additional day.
Feel free to return should you have additional questions; we are here if you need us.
Have a magical time!
Raquel