I sent this to a friend of mine whose young son is interesting in learning about programming.
Hopscotch (https://www.gethopscotch.com/) is a coding app for the iPhone or iPad. It looks pretty cool.
Scratch Jr. (http://www.scratchjr.org/) is an app to help introduce kids ages 5-7 to programming. It runs on tablets.
The full version of Scratch (https://scratch.mit.edu/) is a bit more powerful, but requires a PC. It’s for kids ages 8-16.
Code.org (https://code.org/) is a good resource, but there’s a lot of stuff there.
You can build real games with Stencyl (http://www.stencyl.com/). It’s kind of advanced but it might be a good option if he outgrows some of the simpler teaching tools. I would have gone nuts on this if it had existed when I was a kid, but I was a weird kid.