Hi Haley. Thank you for reaching out to planDisney with your question.
So you are looking at staying at 
Disney's Grand Floridian Resort & Spa? I just stayed there this past March and the newly renovated rooms are just beautiful. The 
Mary Poppins theming is subtle and classy, the space is so smartly designed, and it is definitely very grand. Plus, you are also planning to come to the 
Walt Disney World Resort at a great time. If next year is anything like this year, the 
EPCOT International Flower & Garden Festival should be running (this year, it's from March 1, 2023, to July 5, 2023) and the food at those 
Outdoor Kitchens is mouth-watering! Not to mention the 
beautiful topiaries and flower displays throughout the park. Stay tuned to the 
Disney Parks Blog for announcements about next year's festival and when 2024 dates will open for booking.
Currently, there are two 
spas open at Walt Disney World. There is 
The Grand Floridian Spa that you mentioned and the 
Mandara Spa at the 
Walt Disney World Dolphin Hotel. While more may open between now and the time your vacation arrives, these are the only ones open at the time of this answer. Massages and services are an additional cost to your resort stay. You can visit the websites for these spas to see a listing of services offered, the cost, and the ability to book a reservation. I think a massage would be a wonderful activity for a rest day in the middle of a vacation or a nice way to end a busy park day!
Haley, I love how far in advance you are planning this vacation. I'm the resident planner in my family and I can tell you from experience that it makes all the difference! Be sure to 
check out all the new offerings coming to the resort. While these additions were announced for later in 2023, there's a good chance they will still be available when you come in 2024! Not to mention the surprises that are in store for us that Disney hasn't even announced yet. I'm sure they've got lots of them up their sleeves!
Be sure to 
reach out again in the future should have any other questions.
Today is a good day to try,
Matt