Hello, Cheryl! Thanks for bringing your question to planDisney!
It sounds like there could be a few options for your situation depending on which ticket you use to upgrade to a
Magic Key pass.
If the separate Park Hopper ticket that you mentioned hasn't been used to make any theme park reservations, then you can upgrade that particular ticket to a Magic Key and not risk any theme park reservation cancellations. Your other tickets and park reservations will remain unchanged. You will need to visit a ticket booth at the parks to upgrade this ticket to a Magic Key. If you choose to upgrade one of the tickets for which you currently have theme park reservations, you will lose those theme park reservations unless you upgrade on the last day you use those tickets. For instance, if you have a three-day ticket and upgrade to a Magic Key on day one, the theme park reservations you have made for days two and three will be canceled. This could be risky because there may not be any reservation availability left for those other two days or, depending on the type of Magic Key you select, those days could be blocked out.
If you upgrade your three-day ticket after you have entered the parks on day three, however, you will have kept your theme park reservations in place and you'll be able to easily upgrade your ticket to a Magic Key in the
Disneyland app. Just be sure to upgrade before the parks close on that last day.
Since you can only upgrade one ticket to one Magic Key, I suggest you choose the ticket that has the higher value so you can maximize the amount being put toward your Magic Key. Keep in mind that California residents are able to purchase a Magic Key with a monthly payment plan and this option is still available if you upgrade.
I hope this information was helpful! Have a magical day!
-Linda