Hiya, Jim!
You can absolutely purchase a one-day, one-park ticket with Genie+. There, that was easy!
As you are planning your trip to
Walt Disney World, the first thing you may want to do is verify that the
theme park you would like to visit has a reservation available. It looks like you're planning to visit on a pretty busy theme park day, Jim, so before you buy the ticket, check the
theme park reservation calendar to make sure you can still
book a reservation.
When you
buy your theme park ticket, you'll be walked through step by step how to get it done the way you want. The first page will just say Standard Theme Park ticket, but when you click continue, you'll be asked how many days you want, what days you are visiting, and whether you want a one-day, one park ticket or one with a
park hopper option. It will give you a total, but move on to the next screen. That's where you can add
Disney's Genie+ Service.
Jim, I can't imagine there is a more magical place to be to celebrate the Fourth of July holiday. Drink lots of water, pack your patience, and enjoy a practically perfect visit!
Anna