Hello Rob,
Thanks for stopping by
planDisney with your question. Before you know it you'll be joining
The World's Most Magical Celebration! There is so much to see and do, and everything looks especially beautiful right now with
EPCOT International Flower & Garden Festival in full bloom, and the
Beacons of Magic lighting up each night in all four parks.
Disney's Genie+ is a helpful add on, even in parks where the standby lines aren't too busy, it gives you more time to stop and enjoy the amazing entertainment each park and slow down a little to enjoy more magical moments.
Genie+ selections cannot be modified at this time. It's very possible that you may make a Genie+ selection for a ride and then see a better time pop up. While you could cancel your existing selection and book the new time, I wouldn't recommend that. In the time it takes you to cancel an existing Genie+ selection, the new selection will most likely be taken by other guests. To me, it's not worth the gamble.
Prioritize attractions that are important to you. If you're going to
Disney's Hollywood Studios and riding
Slinky Dog Dash is on your "must do" list. Make that Genie+ reservation at 7:00 AM and take whatever time you get, or plan on hopping in the standby line as soon as you get to the park and make a Genie+ selection for another attraction. It helps to realize that even with Genie+ you'll probably still use the traditional standby lines for some attractions. If this is your first time using Genie+ it may seem overwhelming, but once you are in the parks, you'll get the hang of it pretty quickly.
Hope this helps. Enjoy planning your magical vacation!
Diane