Couldashoudawoulda, thanks I'll be in touch.
Teaching Nicholas to ride a bike has been such a desperately unsuccessful thing so far. He has a scooter, but it doesn't really help to translate balance to a bike. But pedalling, steering, braking and not falling over is not likely. Too much to deal with, and ends in tears as a result.
I took him out on the Puky and he dwarfed it, but did his best, bless him, and loved it! I felt so guilty as it is obviously so small for him. I have his old bike,which is a little Giant, and I could strip it down to bare essentials just to help him get a start, but I just feel the proper balance bike would work so much better, the weight of the giant and the little wheels won't help.
Also, I have no idea if Nicholas will ever progress to using pedals too, who knows. Part of the fun of parenting I suppose.
I'm wondering if we had a similar bike to yours but extendable maybe (in a secure way in the down tube) and then use disc brakes which wouldn't matter if he started with 20" wheels. It would look odd, but it would provide a foundation which could size up as he grows.....
damn they grow fast!