The shop I work in is kind of in the same boat. I have been using standalone ProAnimator and then have to import the videos in AE CS5 to put it all together. A few extra steps but I am able to get done what I need to.
I know Serpentine and Reflector work on MAC AE CS5. Reflector doesn’t really help until ProAnimator works though.
Hopefully ProAnimator, Invigerator, and the rest of their products will work in MAC AE CS5 soon.
Chewie