Hey there David,
Welcome to planDisney and thank you so much for your question! I'm happy to hear you'll be making the trip over to the Happiest Place on Earth early next year.
Currently, there are two periods of time where Guests are able to add on
Disney Genie+ Service to their Disneyland Resort
theme park tickets - at the time of purchase or after they scan their ticket into the parks during their trip. This applies to all Guests regardless of where they reside.
I've added Disney Genie+ Service on for trips using both methods, personally. From my experience, it is very rare for Disney Genie+ Service to sell out and become unavailable, though it is subject to limited availability.
My recommendation is to try to arrive in the parks as early as possible on the first day of your trip and as soon as you step through the entry gate, you can pull up the
Disneyland Resort mobile app on your phone. On the home screen, you'll see a banner for the Disney Genie+ Service near the top that you'll want to click on and it'll walk you through the steps to add the service for your trip.
It's such a huge convenience to have this service during your Disneyland Resort vacation, but one of the extra features I find that not everyone is aware of is the
unlimited digital downloads of Disney PhotoPass photos! When visiting with friends and family, we make it a point to stop by as many Disney PhotoPass photographers as we can to take advantage of this feature and we end up with a whole photo album to document those new magical memories!
Thanks again for your question, David. Have a fantastic trip!
Wishing you a Magical Day,
Greg