Hi Darr,
Thanks for visiting Disney Parks Moms Panel.
A trip to Walt Disney World is always pretty exciting in itself, and I can just imagine that seeing your granddaughter perform with her junior high school band will make the trip even more magical and memorable.
The
transportation options for getting around Walt Disney World include
Walt Disney World Bus Service, water transportation, Monorail, and
Minnie Van Service. Together, these transportation options can easily get you to just about any destination within Walt Disney World Resort. It sounds like you have a need for transportation outside Walt Disney World Resort. While I don't have the details on the other hotel or its location, I'm thinking the options to get there would be a rental car, taxi, or a car service such as Lyft. I'm sorry that I don't have better ideas that come to mind. My best suggestion is to check with the Front Desk at your Walt Disney World Resort hotel and perhaps with the details they might have additional options to recommend.
Darr, here's wishing you a wonderful stay at Walt Disney World and a fun time watching the band performance!
Jerry