Since I have no idea how he un-governed the cursed thing, and I'm not "bored" enough to try to reverse the procedure, the kids are now free to zoom around our driveway and yard at speeds approaching 5 mph.
Apparently, speed has actually improved Sarah's driving.
Except in this case.
Will is still hopeless, even on a zebra scooter. Ah, well. At least they've got about 13 years to learn to look in the general direction in which they mean to proceed.