I read it differently. In your opening post you said "like in the next 5 years ...". I understood that to mean 2017, 2018, 2019, 2020, or 2021. If you don't plan on doing this for at least five years, it does open things up a bit. I'm not saying it'll be okay then, just that possibilities exist.
Anyway, it's not for a bunch of strangers to tell you how to live, or what choices you must make. Five years from now, your desire for a thru-hike may have morphed into something else. It's also possible that your wife will become comfortable with the idea of you hiking before the kids are out of the house. So maybe some compromising...?