I'd go with Python, Javascript, (and also Godot engine if they have an interest in game development). After that, any other language they'd want to learn shoul

I'd go with Python, Javascript, (and also Godot engine if they have an interest in game development). After that, any other language they'd want to learn should come fairly easily to them. All three have great huge piles of tutorials available free on YouTube, as well as various free and / or cheap resources available from Humble Bundle, Udemy, and other sites (especially if you catch them on sale).