I would highly recommend getting the handbrake. My 4 year old can effortlessly squeeze the handbrake. He loves to bike super fast and then brake right before he is about to hit you. We took him to the pump track and he was the youngest, most confident kid there. He could easily maneuver and control his bike without any fear.

This bike fits perfectly, is very stable and the beefy mountain bike wheels make off road terrain doable without sliding out. My toddler fell in love with mountain biking because of this bike. I tow him up the hills with the tow rope (which was much easier than Inthought it would be) and he shreds down!