When we bought passes in 2010, I heard about people being asked to eat their sandwiches outside. The only item we've ever been asked to leave outside or discard was a disposable straw (juice box).
We never had trouble with food for our littles in a diaper bag. Even without a diaper bag, I always have some dry snacks (like PB crackers or cheez-its) to stave off crankiness.
One time during early June when the park closed at 7pm, all food was closed on the shamu side of the park an hour before closing (which is when the last shamu show happened). My blood sugar was crashing and there wasn't anywhere to buy food at that time. I walked up to the pretzel place only to find the door locked. I knocked but had to watch from outside as the employees throw out everything left in the case.
Since then I always have a granola bar or two on hand to avoid headaches and crashes! We do enjoy the refillable cups (which also work for 99 cent slushes), and use an annual pass dining plan often.