Hi Pam,
How wonderful to be taking your granddaughter to Walt Disney World for her first trip! You arrive so soon - you must be getting really excited!
Yes, absolutely you can have your Disney Resort Hotel hold your bags for you if you arrive before your room is ready on your check-in day. Simply ask Bell Services to hold the bags for you and they will be there safe and sound for you when your room is ready.
I love that you already have a plan for that first day.
Disney's Animal Kingdom Theme Park is such a beautiful place to spend a day. Some of my family's favorites there are
Kilimanjaro Safaris, on which you can see amazing animals as you ride through fabulous settings, and
Finding Nemo - The Musical, which tells the Finding Nemo story with wonderful music and larger-than-life puppets. I am sure that you will have a great first day at Walt Disney World!
I hope that this information is helpful for you, Pam. Please do let us know if you have any further questions!