When you're out at the parks, you'll need to bring a few things with you. Typically we get a locker and it really helps. But I also have to have things on hand to make my trip easier.
Everyone will need basics:
Advil, Tylenol (pain reliever)
Money - cards and cash
lightweight jacket for evening
Growing up in Los Angeles in the 70s/80s we visited Disneyland on a regular basis and often after school, before "Annual Passes".