Okay, I read this on another board but I have no idea where so I can't give credit where credit's due. But a guy told how he taught his son to ride a bike -- w/o training wheels.
He took off the training wheels and the pedals and crankshaft, and lowered the seat so the kid could put his feet on the ground. He let him push that around for awhile with his feet.
Then he took him to a parking lot and told him, "I'm going to push you, and you see how far you can roll without putting your feet down."
At first, the kid would put them down and stop himself immediately. (Obviously the goal isn't to push hard!) Then he'd roll a little farther, and a little farther, until the dad could push him and he'd keep his feet up and roll all the way across the parking lot until the bike stopped and he put his feet down.
In other words, he learned to balance/roll ... and after that, it was just a matter of putting the pedals back on and he was off.
Sounded like a good plan to me.