Not going to be easy im afraid. may i ask what the target is for the scene. render or export? if its render you could point cache the skinned meshes. I would avoid scaling rigs unless they were designed for it. Object level scaling usually send them into a seizure.
You might be able to do it by exporting the whole thing through FBX and setting a scale factor. With FBX you can have it "bake" the animation (i.e. one key per frame) to get around rig/IK problems. Of course that is assuming you don't need to edit the file again after scaling it.