Hi Mike and welcome to EKN and the sport. We’re going through it right now with our 4 year old grandson. I can tell you what we’ve done that seems to be working so far.
Age 2 we started him off with electric cars around the house. It taught him the basic concept of go and turn.
Age 3 we moved him up to a bigger electric car for outside.
Age 3 1/2 or so we got him going on Mario Kart. It’s good and bad, it helps to teach driving on a “track” but it’s also a contact sport in the game.
Age 4 we put him in a CRG puffo and started straight line stuff with a strap attached to the back of the kart so he couldn’t get away. What you’re teaching here is go and stop, more stop that go. Kids are born knowing where the gas pedal is LOL
At 4 1/2 we put him on the track with a throttle stop so the kart only goes about 20-25 MPH. We let him go as long as he wants which is usually about 30 laps or so. He can now very smoothly go around the track but we won’t turn it up any until maybe the fall.