Regarding the handbrake issue; Depends a lot on the terrain. Robbert's comment brough back a memory of scary moment;
When my boy was about 4 he was cycling without problems in Holland. Then we loaded up and went to France for a holliday. He went down the first hill he ever saw, on a gravel road. Accelerated, his feet came off the pedals, handbrake didn't work, he couldn't stop anymore. It ended in a mighty crash and many tears. I felt very stupid and very lucky he escaped with cuts and bruises. Brakes need to work. Cheers JJW