My DH and I always bring a backpack with us. On our honeymoon in Disneyworld, some days both of us had a backpack, typically when we're in
Disneyland, we only need one bag (it's alot easier in Disneyland when we stay on property to "run" back to the room then Disneyworld).
Our backpack's have always been able to go on the rides with us. DH carries a normal backpack (we got it at costco), and I carry a smaller backpack I picked up at AKL last year, although I need to get a new one because DH ruined it on a trip he took with his brother to Disneyland- but I digress.
I strongly recommend the backpack. This comes in handy when you make smaller purchases to throw things into your bag. Also, we would freeze water bottle's and throw them into our backpacks to have cold water throughout the day (it was June on our honeymoon).
I do wear my passport/KTTWC in a lanyard. I typically have that and my photopass card in the lanyard ready and accessible. We normally have a point and shoot camera, though this trip we're taking our new DSLR and 2 lenses and removable flash- so I'm looking into a camera back pack for this trip.
I also recommend bringing your sunscreen with you. Buying it in the parks leaves you with little choice and high $$$. We also tend to throw in some snacks because I'm a big Kashi fan, and like to sometimes grab a non sugary/salty snack
I also pack an extra shirt (t-shirt if I'm in a tank top, tank top if I'm in a t-shirt) and a hat.
Don't know if this is more info then you're looking for- but it's helped me. My main point is, backpacks are awesome and totally fit on all rides, usually in the basket they have or tucked in between your feet.