There are two shows nightly, one at 6:30 p.m. and one at 8:30 p.m., but no matinees. If you're at the early dinner you go to the late show and vice versa, although you could do alternate dining arrangements (Palo, Beach Blanket Buffet, Pinocchio's, etc.) and catch the show of your choice.
I believe there's no set schedule for which night the show runs. On our November 4-day it was on the last night, but I've seen people post other show schedules for the 4-day.