The Predator 212 is a lot of engine 

The Predator 212 is a lot of engine for a kid, but with proper gearing and a clutch mod or two you can tame it for a responsible kid, or yourself.
1) a smaller rear sprocket (60t) will take some of the power out of the take off.
2) a larger clutch sprocket (14t) will do the same thing
You're thinking this is a recipe for speed and it is, but you still have the governor on it and there is a "high-end" adjustment screw on the linkage, so you can limit the maximum rpm's to be even less than the governor's 3600. Just screw it in and the linkage stops the acceleration where you say.
3) finally, if you're still not satisfied you can change the clutch spring. I think standard clutch engagement is around 2200rpms. A beefier spring will push engagement up to 2500, and the beefiest 3100. This means full engagement. Less rpms than that and you have slip, all the way down to complete disengagement. The spring is why the bike gets away from you, when you want to start moving. If there were MORE slip, you'd ease your way into riding off. The only drawback being wear and tear on the clutch pads, you'd have to replace the clutch (or pads) sooner.
Take a look at what I was able to do with my Predator 212. The take off is very smooth (anyone could ride it), Before the mods it ran right out from under me. Here I have a 14t clutch, 60t rear sprocket and a black clutch spring (3100) I was going for a smooth start and a lot of speed. I have removed the governor and modified the engine appropriately, also I turned the high-end adjustment screw OUT. To limit the rpms (and top speed), turn the adjustment screw IN.