If they can ride training wheels and have for awhile, they are probably ready to ride without them. I threw my kids bike in the car and went up to the local soccer fields. The area has short grass and lots of space. I made sure he could reach the ground with his feet and gave him a push. Never fell once.

I had another kid who had his granddad take the training wheels off one day he was over and when grandad turned around, the kid was gone riding his bike. The third kid couldn't stand his same age brother riding without them so he made granddad take his off too. He fell once and was skittish for about 15 minutes but when his brother zoomed by for the 3rd time, that was enough and he took off too.

If they fall, don't look scared....just encourage them. It will happen.