A very warm welcome to planDisney, Christine!
At this time, no announcements have been made about Easter Mass being held. I recommend checking
Disney Parks Blog a little closer to the time for the latest announcements. Historically, Mass announcements have been publicised in the Main Lobby of Disney Resort hotels, so you could also speak with the Front Desk about any services and their location. There is no procedure to follow, and all Guests are welcome to attend.
I'm sorry I haven't been able to provide a more concrete answer today. That said, some Churches close to Walt Disney World already have their services listed. The Mary, Queen of the Universe Catholic Shrine, for example, welcomes many visitors to the area for Mass.
Once you have celebrated Mass, the Easter activities can continue throughout the Disney Resort hotels. There are typically the most spectacularly decorated chocolate Easter Eggs in
Disney's Beach Club Resort lobby, and some chocolate creations that will have you second guessing if such delights can possibly be confectionary in Disney's Grand Floridian Resort & Spa. There are Easter activities in the Parks too, such as the Easter Egg-stravaganza Scavenger Hunt in
EPCOT.
However you spend the day, I wish you and your loved ones a wonderful Easter celebration, Christine. Please pop back to planDisney if we can help with any other questions.
Louise