My toddler minibike training technique has always started with making them start and stop multiple times on my command with me following/hanging onto to the back of the seat. Once I feel relatively confident that they have that "seemingly simple" skill set down pat, I turn em loose in a large open area for some down and backs with each loop consisting of a full stop back where I am standing. After they can do this without issue, I let them shift gears and repeat the down and backs. At that point, I turn em loose. I have used this simple technique many times over the years (with my girls and with friends and families kids) and have never had a kid hit anything or end up in the pond.
I have heard of many other folks who have simply put a kid a minibike and next thing they know, the kid runs into a building or a parked car.....It all comes down to the kids first learning which way to twist the throttle and how to apply the brakes. I also have on occasion noticed that some kids actually "forget" or do not have enough sense to put their feet down when coming to a stop or while manuevering slowly. Once again, the key is to make them start and stop numerous times until that seemingly simple tasks becomes "natural".
I am sure you are past all that business by now Lendaddy and are probably schooling him on how to sit down to preload prior to hitting a hairy double right out of a corner.