Hi Heidi,
Welcome to the Disney Parks Moms Panel. I am so happy to hear about your upcoming visit to Walt Disney World Resort, I am certain you are going to have a magical time!
The best way to get from Disney's All-Star Music Resort to
Disney's Grand Floridian Resort & Spa would be to take the bus from your Resort Hotel to Magic Kingdom Park. From there, you will have the option to either take the Monorail to the Grand Floridian Resort & Spa or take a boat. Once you exit the bus area, walk toward the entrance to Magic Kingdom Park and follow the clearly marked signs toward the Monorail or Boat launch.
Given that you will need to take two modes of transportation, I would highly recommend giving yourself plenty of time to arrive at your destination. We typically will leave an hour and half prior to our Advanced Dining Reservation when we have to take two modes of transportation, just to be safe.
If you arrive early for your Advanced Dining Reservation, that's okay. After you check in, I would suggest taking the time to explore the Resort, it is absolutely breathtaking! There are plenty of spots for pictures, and lots of fantastic shops to browse.
I hope you have a great time at Walt Disney World Resort, Heidi. Please let us know if you have any other questions, we are always happy to help.
Stephanie