I would suggest riding MMRR first and seeing if you're okay. In my mind, MMRR shouldn't give you issues - there's no 3D to deal with. But if it did give you issues, I might pass on Remy.
Remy, for me, was mostly okay. A little bit of motion sickness afterward, but not terribly so.
There was one scene that caused me the most issues. While trying not to spoil anything: there's a section that's reminiscent of the scene in the movie when Remy is running through the walls. (It's later in the ride, and should be relatively obvious that it's coming.) The 3D imagery during that section was really close to the vehicle, and the quick movement on the screen caused me some issues. If you can either close your eyes during that section (or maybe one-eye it), it'd probably help.
Some folks reported issues with one spot earlier in the ride where the vehicle does a 360 spin. I got around that by using that move that ice skaters use when they spin - I kept my head (and eyes) facing the screen until I couldn't hold it there any longer, then turned my head all the way around to face the screen again. No issues for me with that.