I’m not the best judge of ages of youngsters but if I had to guess just by looking at it, I would say he is a bit younger.
For some reason I’m pretty good guessing childrens’ ages (years of babysitting?). The Waikiki and trike photos look no older than 4 to me, I supposed if he was a slow grower might be 5, but the trike photo almost looks a little younger than the beach photo. I would vote against 6 for sure. Six year olds are usually starting to get a bit gangly.