Oh, yes... the bag topic. I researched and researched and researched this. I tried on Baggalini bags, and went back and forth about ordering an ebags Piazza Day bag.... but then I came across a perfect one for me at Target in the travel section!
I used this one 2 weeks ago for 9 days in the parks:
http://www.target.com/p/Swiss-Gear-Shoulder-Bag-Sling-Grey/-/A-13273307#?lnk=sc_qi_detailimage
(It was only $19.99 in my store last month.)
I put my KTTW card in the front zip pocket, my maps and times guides and any notes in the back zip pocket, and everything else went inside. I had my camera in one of the side pockets so it was easy to get to, but secure on the rides, and the other side pocet held a water (which I didn't drink that much of - the free ones from a QS place were fine.)
I was wonderful to take on anad off during dinner, very compact, was comfortable wearing all day, and was very easy to either keep on or stow on every ride, except everest.
We did get caught in a downpour and a couple of docs got wet in the front pocket, but otherwise were ok.
It was really great for the plane ride too. Boarding passes, kindle, snacks... all fit inside. And it worked well with the backpack I wore through the airport as well. (held DD's PJ's - late night flight - my DIS travel planning binder.)
I also kept trivia sheets in the rear pocket and pulled them out when we were waiting in lines, etc. It was fun, easy to get to and easy to put away when it was our turn.
I also found that switching to a "business card holder" for vacation was a terrific way to keep my KTTW card, DD's KTTW card, Insurance card and driver's license (so I could order adult beverages.) Everything else, I left at home.

It was a great way to lighten the load, and I haven't really switched back yet, even though I've been home for almost 2 weeks. ha ha!