Like learning to walk, bike riding for most is a process that simply takes a while. Most kids learn with training wheels on, and it is definitely a nice way to get going so that your child gets the "I'm a bike rider" feeling straight way. But I am sure we all have seen plenty of kids leaning over as the training wheels inevitably weaken on one side or the other. Training wheels are not made with the same integrity as the bike itself. What really matters is getting the rider up to balance speed so that trainers aren't needed, and then knowing to put the feet down when they slow down. (Seated, kids should be able to put both feet to the ground so please keeps seats low). One thing to remember about training wheels is that they are for training: once the pedal action is learnt and balance speed is achieved, training wheels soon have no place.
In the real world however, every new rider goes through the learning process differently. Confidence is King. Do whatever it takes to keep them confident but please note training wheels often feel wobbly and precarious to a new rider, feet on the ground is much more reassuring. Often in the process of learning, a child will have to go between having training wheels on, having pedals off, having pedals on, pedalling with your help, and back to trainers on, until the balance speed and confidence is found.
A good way to introduce pedals and no training wheels is to utilise gentle down slopes that give just enough speed to balance, then when it flattens encourage your child to keep the momentum by pedalling...and often they are away.
Warren Key, Melbourne bike retailer and designer of ByK Bikes for Kids