This is a very common thing for people to want to do now a days. I've read about it (usually in the context of some type of travel hacking) and the number one thing that everyone who's gone on trips like this say is to go on a shorter trip first. From what I understand, it's very common for people to get this idea into their head, then two weeks in decide that they are already done. So while I don't want to discourage your dream trip, I definitely encourage renting something for say two weeks, and try a trip of that length first. This will give you a MUCH better idea of what you want in a rig without committing you to anything. It's not uncommon that people do this and change their overall plan to mix things up (maybe we'll stay on a house boat for a month, then rent a tiny house for a month, whatever). Anyway, just an idea before sink a ton of money into this.

Advice freely given without knowing anything about you or your family. Maybe you regularly go on months long trips and are already hardened travelers; most people aren't.