I believe Chess.com has a sister site that is more kid-friendly. Can't recall what it was called but that seems like a one-stop shop for your son's continued progress with chess ...
If you'd prefer face-to-face chess training, you'd essentially want to balance "playing games" while playing close attention to the kind of mistakes he's making .... these provide data points you can use to provide lessons suited to his needs.
Tactical exercises and basic endgames can be quite fun. You might look into chess mazes (which do wonders at improving visualization for kids starting out) as well for productive exercises.
I believe there's a website called ProfessorChess with some remarkable handouts and instructional material used for teaching.
Once he's regularly beating you during your "play" sessions and ASSUMING he's improving by leaps and bounds, you might want to consider getting him a coach.
I am an average player at best. I am regularly destroyed by the computer on this web site. Love to play though. I am introducing the game to my nephew and he is exceptionally bright. We played on a computer and he seemed to enjoy it. He was playing on the second level before the evening was over, but had the squares light up to show him his possible moves. He left today, still asking questions, and I feel he will be interested in exploring the world of chess. Would like some advice on how to proceed. He is 10 years old.
Lee from Cincinnati