nice. preferably anything OS specific would be linux and macos new machine is a macbook air

I'd say go Linux, maybe even no DE terminal only to start off. Teach them bash then build from there. Kids easily get sucked into computer = videogames and thus never learn how they properly work and how to create with them thus starting from the ground up may give them a greater respect for computing. Too many years of my childhood wasted on games when I could have been linuxmaxxing or codemaxxing.