I like this idea, but I think you should work a bit of history/philosophy into each lesson by explaining why things work the way they do. The students are unlikely to engage with a history of a system they've never used before, so starting with that will lose their attention before you've even gotten it. Giving them a bit at a time means that they will slowly build a mental model of how *nix works and is built.

Hot tip: if your skylight gets smashed in by hail or branches during a storm, you can use an umbrella like this to keep most of the rain out until you can get it repaired.

OSM for day hikes and Avenza for anything more serious.