My son got a wooden balance bike when he was about 4, no pedals he just pushed himself, he was going full length of hall in no time with a push from me. He got a Halfords kids bike at 5 and was off in literally seconds, once they've got the balance it's easy for them!
Downside is they're hands are too small to work the brakes...expensive on the trainers front..
Back in the 1980s, my sons had to learn to ride without the benefit of those balance bikes which I don't think were being produced. The balance bikes are really marvellous.
Two of them found it a struggle with heavy steel kids bikes with poor gearing, and the other one just got on and took off on the bike which he rode helter skelter down the street into a bus shelter. That stopped the little smart ar se!
He was three.
My grandchildren have all had those wooden balance bikes and they really make quick progress. No need for the daft side wheels either. They ride instinctively and it is a far better idea.
Taking off the pedals on an ordinary bike is a great idea. Wish I'd thought of that.
The other bummer for small kids is the massive weight of many of these tiny bikes in relation to the rider's size and power. They are made cheaply of terrible stuff in the main I think. This is why so often you see hassled parents carrying a heavy steel bike and dragging a whinging youngster behind them.