Hello, Colleen! Welcome back to planDisney!
Purchasing a
Magic Key pass is the perfect way to enjoy the splendor of the Disneyland Resort all year long! If the ticket you have for your December visit is a non-promotional, unused, and unexpired ticket, you should be able to apply the cost of that ticket to a Magic Key--this is called upgrading.
The best way to upgrade your ticket is to visit in December with your regular theme park ticket as you normally would. Then, on the last day that your ticket is valid (usually the last day you visit the parks), upgrade your ticket to a Magic Key in the
Disneyland app after you enter a park but before the parks close that day. This way, you can keep any
theme park reservations you have in place for your December trip. If you were to upgrade your ticket at a ticket booth at the beginning of your trip, any theme park reservations you currently hold would be canceled. Just be aware that if you are upgrading a multi-day ticket, your Magic Key activation/anniversary date will be retroactive to the first day you used your multi-day ticket.
Since you are a California resident, you can choose to pay for your Magic Key pass through monthly payments after a $179 down payment. This option is still available when you upgrade an eligible ticket to a Magic Key. Or you can opt to pay the difference between your ticket and your new Magic Key pass in-full.
I hope this information was helpful. Have a great time at the Disneyland Resort!
-Linda