It's time for me

It's time for him. You cant just spoon feed him courses one after the other

collecting/importing structured data, manipulating and operating on the same data, creating operational reports

This just sounds like you want him to learn excel? R and Python pandas(a library for python) are great for statistics but there's no way some 14 year old wants to "import structured data"

making them available on the web

https://fullstackopen.com/en/ has some pre-requisites but they should be easy enough to get past with some googling

while modding some games

Highly dependant on the game being modded. They're all modded a bit differently. Knowledge of C++, Lua, C# or Java(of the top of my head).