I think you should absolutely follow your creative pursuits and inspiration.
I would at least get the project started, and begin compiling your photos as well as flesh out your concepts for the book and I imagine it will grow more organically from there. I'm not sure if you are saying you want to write a photo technique book, which would be useful and go along with your second stage of plans, it could even act as a supplemental guide for your tours. The idea of adding a more journalistic approach would make it something more personal and different entirely. You could also do both, and see how well they mesh together. As a technique book, I would maybe add some basic information, but as a journal it could be successful in it's own merit. So consider tow books or just focus on one idea.
One drawback of just making an e-book would be the fact that the buyer of this book would most likely want to take this along in the field with them. Granted, some may have the ebooks, but overall, the printed material seems more realistic and practical.
I think you pursuing your goals is the most important thing. I never regretted making decisions to focus on a career in a creative field, it was the best decision I made.