How do I share (or copy) a velocity envelope from one track to another?

Specifically, I have a composite parent/child track pair (to do the "Pleasantville" effect), but I want to hold the video in the middle for a few seconds. I put a velocity envelope on the parent track to achieve the hold, but the child goes charging right along. Similarly for putting the envelope on the child track. Copying and pasting the envelope from one track to the other did not work well, either.

Little help?

Thanks.