As far as I am aware keying is allowed, but the majority of it has be dynamic.

Becareful on keying something like that, as It may take a little longer or a little shorter for it to get to its destination, this in turn will put out your keyed frame.

I am having this issue at present and am working around it, it may need a little MEL to detect when something touches something else for it to start the small animation

I have another idea around it, thats more dynamic, but be careful with keying as if it goes wrong it will show. I am only using 1 keying session for 10-15 frames to animate the start of mine.