I think that kind of job is going to require some evenings and weekends? Most of those weight loss places are open hours convenient for people who work regular jobs, I think. Working nights and weekends would be deal breaker for me.
The other thing I thought while reading your story...textbook companies hire teachers to show other teachers how to use their new texts. I have a teacher friend who did that for a while after she quit teaching. Part time with travel, but in an urban area the travel might be minimal. She was recruited and didn't have to find the job herself. But that's an idea. There should be lots of opportunities for former teachers--lots of transferable skills.
After 30 years if you really don't want to work full time I'd think there would be plenty of options for part time. This is coming from someone who quit working full time when her last child was born (13 years ago). Over the years I've worked for pay only part-time when we needed the cash, but I don't want to work at all--unless it is something I absolutely love. I love volunteering so that's what I do instead of working--but I set my own hours in that.
You're in an enviable position of being able to be very choosy about what you do with your time (as am I, but you have a more desirable/marketable skill set than I do). Don't rush into something that might quickly feel like the old grind.
Karen