Short version.
One of the local ski hills in Michigan (Boyne Highlands) organized a bike fest and it was a weekend i had my son, so my GF and I dragged him with us.
Day one: Stop at a local freeride/dh spot to do some hike a bike runs and check out a used DH/Freeride bike for the GF. She didn't like the bike, but my son got a little gutsy-er and instead of just pushing up and riding the bottom 1/4 of the trails (mostly "flatter") by that point. He instead pushed up about 3/4 of the way to the top and was riding down and railing the berms pretty good.
Day two: Race day.
Took him to the finish line and showed him the two easiest trails and told him he could push up as far as he was comfortable. Trails are primarily dirt, lots of up and down rollers 1-2 ft tall, 2-3 ft apart ish, with tree roots, sandy loam, no real rocky tech sections to speak of. he loved it and begged me to take him up the chairlift so he could ride.
Finally caved in after my race runs and let him ride the whole trail. Probably 500ish ft of vert, nothing crazy steep, but he was also on a BMX Mini with just a rear brake and handled it pretty well. I was pretty excited to see him be able to make the trails, and in no time flat i'm sure he'll be faster than me.
So as the weekend progressed we ended up with a 12" Kona Hula w/a 50mm fork and 24" wheels.
It's still too big for him, but looking to outfit it more for trail riding for him.
Suggestions?
Would like to find some better tires, a fork that will actually move for him, probably a bashguard and make it a 1x7 drivetrain instead of 3x7, and mount up some mechanical disc brakes for him