Mmm interesting ideas. I don't often animate eyes and mouth - prefering to sculpt them in place with the right expression. Although you could get a simple open/close using bones in Curvy it would probably look more like a Muppet than a living creature as the muscles underneath wouldnot react naturally.
Another alternative would be to use a stopmotion technique and simply resculpt a few (3D) frames between open and shut. This would give the most natural appearance ( Might try that in a tutorial