Hi Kathie,
Welcome back to the Disney Parks Moms Panel And thanks for sending us another question! I am very glad to see that you are looking to book
Tomorrowland Terrace Fireworks Dessert Party in the Magic Kingdom. It is one of my family's "Must Do" experiences every time we visit, I love that we can experience Wishes Nighttime Spectacular, without the crowds!
For booking this experience, I would recommend to start checking around 90 days prior to your arrival, as Disney could start booking as early as that. The booking for this experience is not set in stone like Advanced Dining Reservations where you can book 180 days in advance, sometimes the bookings will become available 90 days in advance, while last year it was closer to 30 days in advance for our visit to Walt Disney World Resort in December. They also tend to release a block of dates at a time, not day by day like the Advanced Dining Reservations. I have found that the reservations online usually unlock at around 6:00am, and the phones open at 7:00am. Keep an eye on the website and check back frequently,, as you may get a magical surprise one morning and the reservations may be open!
Sending you extra pixie dust in hopes that you will be successful in securing your table at the Tomorrowland Terrace Dessert Party!
Stephanie