We're planning to do scrambled eggs and toast on our park mornings, except for the 2 mornings we have park breakfasts ('Ohana and CRT). My kids love scrambled eggs, and they're pretty quick to make, just whiz them around a hot pan a few times - the toast takes longer!
It helps that they are early risers and they like to eat soon after waking. We figure that protein in the morning will keep them going longer than sugary foods, which is why we aren't even doing the cereal thing.