It all depends on your comfort level. DSLRs are pretty resilient IF they are in a padded bag. You could put a plastic bag around it or have someone hold it in the case of Splash Mountain. I took a DLSR with a pro-level lens on all intense rides a few weeks ago (Everest, Space Mountain, etc). I didn't take a picture while on the ride, but the camera survived the ride.
But if you're going to be worried about your camera, that would make a difference. Take care of your comfort level as well as your camera.
For me, the weight of the heavy lens was more of an issue than fear that it would get broken somehow.
Have fun taking pictures, with whatever camera you take with you! There are so many great photo opportunities in WDW!!!