If a child really wanted to do something with a web app or something highly concurrent then sure. However, in my expereince kids typically want to engage in pro

If a child really wanted to do something with a web app or something highly concurrent then sure. However, in my expereince kids typically want to engage in programming to do something particular. Make a game, make some music, etc. I'd probably introduce someone to SonicPi after something like Scratch. That way they can make some music and have some fun while learning some kind of Ruby. It's built to be educational so should be straight forward to pick up following the tutorials and lesson plans. Elixir is a fine language really. I don't think you're wrong in anyway, it probably would teach some useful skills while also being less frustrating to learn than something like C, but I'm not sure there's much point in a child learning a language for the sake of it. They're also less likely to enjoy it.