The setup is on the patio at the back of the amphitheater, behind all the benches. The patio is divided into a smaller area and a larger one. Both areas have railings that separate them from the main walkway running between the patios and the crowds.
View from the big patio to the small one:
View from the big patio toward the stage (the bleachers are below the walkway):
The buffet is set up at the back of the patio:
From the back of the patio looking to the far side of the amphitheater:
The view is OK - the lighting rigs kinda block it but you don't get wet!
These photos were taken standing at the railing, so about as close as you can get (but they were taken with an iPhone, which accounts for their low quality!):
Both patios have a $250 venue rental fee and a $750 food and beverage minimum. The small one holds up to 40 people, while the large one can hold 40 to 100. There is also a $75 setup fee and then a $12.95 viewing fee for each person who doesn't have park admission. ALSO: Fantasmic! has a higher cancellation rate due to weather than IllumiNations and Wishes.
Hope this helps!