I'd say: give the kid a real C64, because that's how I got started. But, today... I'd say Ruby, but Ruby is a bit too chaotic. BASIC would be better in the long run. Processing is easy to learn, and it's basically Java.
The reason I recommend a C64 is because it's BASIC, but you still have to learn certain computer-related things, like the memory model, pixels, characters, character maps, newlines, etc. etc, if you want to do more advanced stuff. Also, if your kid finds it boring, you know his heart really isn't into coding.
