sorry we weren't more of an help, morph.  you need to start over again at frame zero IMVHO.  tell them you can do 60 fps, but it will cost them double, on account of you have to start over.

1. if the animation is 10 seconds long, then you render 600 frames to tiff (start over, lose the old keyframes)

2. import image sequence to quicktime pro at 60 fps.

3. save movie as uncompressed (no codec)

4. let them worry about the codec

5. the reason they hire 20-somethings at google, facebook, apple et al. is because they don't mind trashing something that doesn't work and starting over at ground zero