I can sure understand the appeal of running away to a more wholesome place. My wife and I moved to an island a few years ago, long before my transition. There were advantages: interesting, creative, mostly liberal people, it was away from the rat race. There were disadvantages, too: no jobs, expensive real estate, an expensive ferry ride to civilization. On the whole it was a good move for us, though we eventually moved to a more conventional rural setting, where I am now transitioning.
You have to be really careful what your objectives are before selecting a location. If the objective is for your fiancé to live in "witness protection" stealth, then you could choose almost any community where you were not known. If the objective is to live off-grid, on a back-to-the-land acreage, there are still places where you can do that, though they are in demand, and land can be expensive if it is anywhere close to civilization.
If you choose your location carefully, your kids will not suffer. The island where we lived for a few years had an elementary school, and there were lots of children's enrichment programs that home-schooled children could participate in. You just need to do your research to find the right place.
The important thing is to clarify your objectives. Talk a lot with your fiancé, find out what their goals and priorities are, and share your own.