Hi Mary,
Welcome to the Disney Parks Moms Panel! Thank you for bringing this question to us!
Although I was unable to check for either of these online, I did call to speak to a cast member in dining at 407-939-1947. She checked the
Fantasmic! Dining Package and the
Fireworks Dessert Party at Tomorrowland Terrace times for December 18th but said there was no availability. If you have a Walt Disney World Resort hotel reservation, you could call back and a cast member could check for the dates of your stay. Since I do not have a reservation at that time, she could only check for the 18th.
It may be possible to book, so I suggest that you call in addition to continuing to check online. I am sorry that I do not have more specific information!
As a back-up plan, you could make a dining reservation at
California Grill,
'Ohana or
Narcoossee's. Although the viewing may not optimal, you could still enjoy the Happily Ever After show from a distance, depending on your seats. Be sure to make your dining reservation at least 30 minutes prior to showtime.
Mary, I am sending pixie dust your way hoping that you get to enjoy the dessert party and Fantasmic! experiences during your stay!
Magic, memories and Minnie Mouse hugs,
Donyell