Hey, Kara! Looking over the schedule for these two evening events at Disney's Hollywood Studios, it looks like you are going to have a really tough choice to make. While you could possibly see Fantasmic! and rush quickly out of the Hollywood Hills Amphitheater to view
Jingle Bell Jingle BAM!, you would end up missing the best part of the Jingle Bell Jingle BAM! Dessert Party - the desserts!
In my experience with the dessert parties at Disney's Hollywood Studios, Guests can usually begin checking in for the event about an hour and a half before the nighttime spectacular is slated to begin. Cast Members will then escort party attendees to the viewing location about 15 minutes before show time. With Fantasmic! being shown during the time period before Jingle Bell Jingle BAM! is scheduled, this would leave you with no chance to enjoy using both the VIP voucher for Fantasmic! and the delicious holiday treats.
Since Jingle Bell Jingle BAM! is a limited time holiday event, I would really suggest you make seeing it a priority. It could add so much holiday magic to the upcoming season for your family. If you have another evening planned in this park, perhaps you could plan the
Fantasmic! Dining Package on one night and the dessert party on the other. Keep an eye on updates to the park's schedule in the weeks leading up to your trip. A second showing of Fantasmic! could possibly appear on the schedule, which is usually much easier to attend than the first showing. That could help you enjoy your treats and celebrate with Mickey all in the same evening!
Hope this helps you make a plan, Kara. Please let us know if you have any further questions.
Brandy B.