@mhoye You absolutely need to teach filesystems now (meaning: how files are organized in directories ("folders")) because most kids these days(tm) do not get in contact with regular files any more. And this lack of understanding will make it much harder to teach some of the other concepts.

Also, you need to know about ASCII (and please build UTF-8 on top of that).

Stuff from XEROX Parc doesn't hurt (early computer interaction), early computer graphics (conway's game of life) is always nice.