Not the OP, but I've had some good luck with teaching it to teenagers at the library.
By the time someone is a teenager, they likely have some experience doing algebra, which (I think) makes the idea of a "function" a lot easier to comprehend; variable substitutions and whatnot are kind of confusing to someone who isn't even used to seeing letters in math.
Really positive thus far. We'd done a bit of javascript before in the browser so he had some fundamentals already but it was always a bit distracting to have to deal with the additional HTML and CSS bits, as well as having to introduce the file system and an external editor.
But yeah, the 8 year old had a game up and running the first day, and the 5 year old picked up enough just watching to suggest code changes.
I set up an old laptop to boot straight into fullscreen pico8 so they can just open the machine and get moving. Just like my overly romanticized memories of myself at the same age.
I tried introducing a few "under-10s" to the joys of Pico-8
But it actually requires tons of patience if you really drill down into it
I made the fatal mistake of firing up a GameBoy emulator to show them examples of what they may create and naturally they became obsessed with classic pokemeon crystal instead ;)
By the time someone is a teenager, they likely have some experience doing algebra, which (I think) makes the idea of a "function" a lot easier to comprehend; variable substitutions and whatnot are kind of confusing to someone who isn't even used to seeing letters in math.