Gosh, I wouldn't want to miss out on the great pictures I could have! Last time we went, I brought my baggallini city bag (
http://www.amazon.com/Baggallini-Wo...=UTF8&s=apparel&qid=1295223157&sr=8-2-catcorr) for tickets and whatnot, there isn't enough room in there for an SLR, I didn't want to leave it in the stroller of course, so I ended up constantly putting it in and out of our snack backpack and feeling like we had to bring the pack on every ride with us.
I didn't want to get a holster camera bag because I wanted to bring my videocamera and zoom lens as well, and other camera bags that fit more aren't designed for the kind of other non-camera stuff I wanted to bring, like the kids autograph books.
I ended up getting a zing camera cover:
http://www.amazon.com/Zing-501-101-...AVLO/ref=sr_1_1?ie=UTF8&qid=1295223556&sr=8-1 and a Baggallini Messenger Bag:
http://www.amazon.com/Baggallini-Me...=UTF8&s=apparel&qid=1295223157&sr=8-1-catcorr, which despite its name is really a small one strap backpack.
I've been very happy with this arrangement. The Zing cover protects my camera within the backpack, or if I just want to sling it over my shoulder, however it doesn't add much bulk, its just a neoprene cover. It attaches to my camera strap so when I take it off it just hangs, I don't need to mess with storing it somewhere. I either put the camera in the backpack (in its cover) or hang it around my neck depending on how accessible I want it to be. We then just left the snack backpack in the stroller at all times and I carried just this small pack on rides with me.
The arrangement did start to get heavy after a week of carrying it everywhere, so I didn't bring the videocamera or zoom lens the last few days and that was much easier.
I love the baggallini's, they are so well made, my city bag is 2 years old and I use it everyday at home and it still looks brand new. I used the pocket on the strap of the messenger bag to hold the essentials - park tickets, fastpasses, photopass and disney rewards card for easy access. Works well and is small enough to be easy to bring on rides, etc.