It's the best feeling, encouraging someone to enjoy something you enjoy. I taught a middle aged chap to ride once - from really not being able to, never had, to riding a nice upright Dutch bike, in less than an hour. And last week, I was manning a stand for a local re-cycling organisation when a gilr (late teens, early 20s?) came up and siad she was embarrassed that she'd never learnt to ride, and a friend had just given her a cast off bike and was it too late? We didn't have the resources to teach her there and then, but we told her to pop down to the unit sometime, and someone would help her. She went along that afternoon, and was riding along the riverside path within 30 minutes. I feel great about it, and it wasn't even me that actually taught her.
Maybe, though, the best thing is helping someone with a disability to enjoy being on a bike/trike/rickshaw/tandem - it can be such a breath of freedom. If you want to think about a change in career, and volunteering is a good way to start, maybe have a look round for any organisation local to you that does cycling for special needs.
Helping your missus might be a good way to get yourself into the teaching mindset too - she might be able to tell you what stuff seems intuitive and what doesn't - once you are a regular cyclist, it's easy to forget that it's not all obvious to a beginner...