stop training wheels
A couple of weeks ago there was a intresting article on the dutch news page, RTL news . The did quote a Belgium article saying it is better to start biking without training wheels.
If children start using a balance bike they will easily start riding a bike without training wheels.
We used a wishbone bike to learn our son biking. First we did use it as a trike later on we changed it to a balance bike. It was a bit wobly the first weeks but after that he did go faster every day.
Finn did biked on a 12 inch mini bike without using training wheels.