Comment by estebarb

The reason I started with Linux when I was 9yo (1999) is because we bought a computer and PC Magazine gave away a CD with Corel Linux. So I did what obviously must have been done... thankfully the disk came damaged, otherwise my lawyer dad would have learned the importance of making backups XD.

So, I would suggest: try to get a throwaway computer, give the kid it and an USB with Linux and let them alone. Do not force anything, just give them the tools and a gentle push. Let curiosity take the wheel and be prepared to answer a lot of questions.