If we bring a stroller, we bring a small diaper bag and leave it with the stroller when we go on rides. Of course we don't leave anything valuable in it, just water, snacks, diapers (of course), etc. My wife and I usually each use a fanny pack, in which we keep valuables/essentials, such as ID, credit card/room key, park ticket, cash, etc.
For the digital camera, I have a fairly small one, but its certainly not tiny. I have a case that is just big enough for it and it has a belt loop, so I just attach it to my belt/fanny pack. I also got a clip on sunglasses case to attach to my belt loops as well.
As long as you go light, I'd think fanny packs should be enough. But if you still need a backpack, its still pretty easy to carry it on all of the rides.
When our son got big enough so that we didn't need the stroller, we passed on the diaper bag and found the fanny packs were still adequate. (We now have a baby daughter though, so its back to the stroller/diaper bag for the next trip.)