This may be a little off topic particularly since it sounds like you already have your bikes, but have you considered teaching with a bike that has a gyroscopic wheel.
There is a company that has been producing a gyroscopic wheel for kid's bikes for a few years, but from their website it sounds like they are looking into creating an
adult's bike with a 26" wheel. See here.

To get an idea of what I'm talking about see this video.
I've not actually tried a bike like this, but I find the idea intriguing.