My DD wears her fanny pack, where she puts her camera, room key, money, lip stuff (lip stuff is the most important thing in the pack!), and I use a backpack/pocketbook for our Brita water bottle, my key and money, my camera, our blister care kit, etc.
We used our LL Bean backpack on our first trip, and DH ended up carrying it around. We actually almost left it behind in EPCOT near American Adventure, which is why I now use my backpack style pocketbook intead. It's smaller, cuter, and has its own compartment for credit cards, cash, license, etc., so I don't need a wallet. Also, I can easily shove it under my feet in rides like Space Mountain, or RnRc where there's no room on the seat or I don't want it to go flying.
I actually have two bags in this style, a Vera Bradley one and a Macy's generic, leather type one. I usually bring the leather one, because its smaller.