K.M.
We took the training wheels off my sons bike the summer before he turned 5 because one of them broke. He had basically been riding on only 2 wheels anyway because of how uneven the training wheels were set. So set them really high, or take them off and see how he does. If he doesn't have any problems without them, leave them off. You might want to make sure he has elbow and knee pads, and a helmet for a while though. In NY state helmets are required anyway, even though most kids don't wear them.