I struggled with this question with my kids. The buggers grow so fast and (at least my) timeline for building is so slow- it feels like a crap shoot. Let them muck along with something a bit small or have them struggle for a season with something a bit too big?
I ended up building 8' Wood Ducklings for my kids and it's worked out well. Design specs suggest it could handle a paddler of up to 100#. My daughter is near that weight and this summer I could see that the end was nigh- but I bet we could push it for another season.
Maybe your son would only get a season of paddling in before transitioning confidently to something that will suit him for years to come, but If you've got younger kids that could grow into it, it could be a winner. Super stable even for young ones and more than enough speed, imo.
You specifically asked about a strip design, though. I simply couldn't find anything in this size range that was designed as a stripped kayak. The WD design is S&G, but I had few problems building it as a hybrid. Actually a "strip stitch and glue" hybrid. If you're not familiar- I fabricated stripped panels and cut the hull pieces from them, and stitched those together. I then stripped the deck as you might any other "hybrid" design. While kayaks designed to have a hybrid deck tend to have many more stations, the WD is so small that it didn't really pose a problem. Looks great. I think some people thought I was bonkers for spending the time to strip boats they'd grow out of so quickly, but hey- we've got our reasons.
I'm guessing the conventional wisdom among designers is just what I've outlined here- who wants to spend a bunch of time, money, and effort building a kiddie kayak that will soon be outgrown? Well, I'd bet it's more than you might think. Then again, it's not me taking a gamble on developing new designs for murky markets. ;)
Good luck!

Patrick