Hi Jill,
Welcome to the Disney Parks Moms Panel, my fellow Canadian, and thank you for asking us a question!
From what I understand, previously purchased
Theme Park Tickets must be upgraded in person at
Guest Relations at any Theme Park or at Disney Springs. This means that you can’t add extra days to your ticket online.
Don’t worry - I’ve added days (and other features, like the Water Parks Fun & More Option) in-person after my arrival in Walt Disney World Resort. You don’t have to add the days right away, either. So long as you have at least one day of admission left and you’re within 14 days of your ticket’s first use, you should be able to upgrade or add dates to your Theme Park Ticket without any problems.
Please don’t hesitate to come back and see us if you have any other questions.
Have a Magical Day,
Lynne