When the package info is released, there will be a set of times for each show that are available for booking. For the 5 PM show, it's lunch times. For the next show - it's somewhere in the (guessing) 2:30-4:00 time frame, and for the last show something like 4:00-5:30. We did the last show a few years ago and the latest seating we could get for dinner was around 5:30-5:40.
So in answer to your question, if 12:00 is one of the times included in the 5:00 show seatings, then yes, you could book then, subject to availability.