Oops it's all too big

My client has changed their game plan, I’m new to this stuff and I was wondering if there was an easy way to make everything smaller (proportionately too if poss). I can do this by holding shift and dragging after selecting all layers but I want to do it for all key frames.

Also is there any way to type in the size you want it to be proportionately i.e. make it’s width smaller and get the height to join in.

Also is there any way to just shrink the stage and shrink the elements proportionately or make all elements fit the stage exactly?