I remember that I got into coding around the age of 13. For me, the trigger was a book on C++, written for adolescents. Thinking about it in retrospective, C++ probably wasn't the best language to get started on, and yet, I devoured that book. So nowadays, beginners books on e.g. Python are probably even more appealing. I also feel that book makes a better present than an equivalent online resource, because it's something physical. Of course, such a book would still require that the 13yr old has access to a computer, in order to actually write code.