I am born and raised in Central FL and have been to Disney more times than I can count. Less is more, you don't want to lug around a heavy backpack all day. If you have small kids, ignore the previous sentence I think the most important thing I bring these days is EXCEDRINE!! Sunglasses are also a must. I only use a "wallet on a string" that has enough room for my camera and cell phone. I usually don't bring a water bottle with me, I buy a bottle early on then just keep that bottle and refill it from water fountains. Of course comfortable shoes is a given. That's pretty much it.
