I definitely think find the right group rather than trying to force the guys who don’t like the low fantasy or history into it. It might be some of your main group, it might be some other people or a new mix. Or maybe just you and your son like you said.
Codex combat system isn’t too hard to adapt to more generic fantasy settings, but historical gaming more broadly is another challenge. We are trying to provide a lot of resources for that but we are a small operation obviously. What we have so far is basically late medieval Europe with the assumption that a lot of the superstitions and mythology they believed in was real so we have a little bit of magic and some fairy tale beasts and so on. So effectively it’s more like low fantasy in a historical framework.
We should have a few more narratives here on the forum soon of people’s experiences running campaigns. The monsterberg campaign is a guideline for one way to do it, although it is of course possible to adapt codex to a variety of degrees. We are also releasing an OSR version along with another (low fantasy as opposed to historical) module which will be a little more simplified. We were planning to release that this year, and maybe we’ll make it although we’ve been delayed from our planned schedule about a month by this hurricane. Maybe by around November we might have something.