Take the training wheels, and the pedals, off. Trust me.
Adjust the seat so that your kid can comfortably walk while on the seat and "scoot". Your kid sounds like he really likes it, which is awesome. He will start scooting and eventually learn to pick up his feet when he gets up some speed.
At that point, put the pedals back on.
Training wheels just make a bicycle into a tricycle. They don't train for anything. Kids need to get accustomed to the idea of balancing and moving, and then they are off to the races!
Don't just go with my advice, look at the old posts. That's where I got the idea and it worked with my two kids!