Re: teaching and falling
My wife and I do that from time to time, and it's always great fun. Often our schedules are such that only one or the other of us can go to the dojo on a particular night, but we also take each others classes as often as possible.
Our dojo is small, and we train with everybody - so we take ukemi from our students all the time. I often take ukemi from my students when I'm teaching so I can feel what they are doing (or not!).