I think this kind of training is a very good idea.
However I doubt that leaving your "other half" with an instructor is necessarily the best way to go about it.
Firstly, if you own a plane and fly it regularly, unless it is a dead common type you will know more about it than any instructor you are likely to find. Do you really want some ATPL hour builder with 200hrs climbing into your plane? Most I have met know nothing about engine management, for a start.
Secondly, the conventional PPL training methods are sometimes very stressfull (deliberately so) and not ideal for teaching somebody how to fly a plane and land it safely. The very last thing I would teach somebody is how to fly a circuit, for example. What they should know is how to engage and operate the autopilot, how to call up ATC, set 7700, etc. And how to do a landing on a nice big long runway. For a lot of that stuff, one can produce a checklist.