Have you ever been responsible for a two year old? Sometimes it seems that they can do things while approaching the speed of light.I HAVE had a few concussions from things other people did. Some intentionally delivered and some accidentally happening. Mostly in situations where one would not normally be wearing any protection. And most of them when I was an adult, not a kid. There are some rather nasty folks around, and a few rather careless ones as well.
The perforated helmets for kids seem to have a fair amount of ventilation, but they don't do much to keep the sun off. So I am wondering what a two year old does that requires a helmet. All of the two year old kids that I know seem to be quite well supervised so that they do not get into situations needing a helmet.
Take a sip of water and they can climb up on a table. During the time you are trying to get them down, they jump off the table, yelling “Batman” and land on their head! Or they are in a riding car, powered by their feet, get their feet caught beneath the seat and fall over, landing on their head.
A helmet wouldn’t help the first case, because the danger isn’t anticipated. But, I present it as an example of the challenges supervising a two year old. The second case is more obvious.