A few others I’m aware of but less familiar with:
http://tutorials.codebar.io http://howtocodeinhtml.com http://learnlayout.com
At this point, you can practically build basic webpages with just HTML and CSS. From here, you can take 2 paths: A graphics designer or a front-end developer.
A graphics designer leans more to design rather than building apps. This requires a basic of jQuery, but mastery of Photoshop. A good place to learn is reading articles from Smashing Magazine http://www.smashingmagazine.com/
A front-end developer leans more to app-building rather than design. This requires knowledge of JavaScript libraries and best practices. For this, select your basic set of frameworks and master them. Suggestions range from jQuery, Bootstrap, to full-fledged frameworks like Ember and Angular.
As for the gamification, https://codecombat.com/
Their HTML / CSS ones are paid, but they have a free Javascript intro one: https://www.codeschool.com/courses/javascript-road-trip-part...
The difference is that Codecademy doesn't have the video beforehand (you read the instructions and do the exercise), vs. CodeSchool which gives a bit more of an in-depth explanation then you do the exercise.
I guess it comes down to which method of learning your stepson prefers.