My 2y5m old boy has one of those three wheel micro scooters, and he's really quick on it. A few weeks ago we were on a short trip and he wizzing along, me running alongside, when he suddenly steered off to one side and stright into the corder of a brick gatepost. I hears a terrible crunch, blood everywhere, but fortunately there was no loss of consciousness and he was fine. It had to be glued, and he has a fine scar on his forehead.
So, I have no doubt that he needs a helmet. I know some people think otherwise, but this experience has shown me that these little scooters give toddlers the ability to go much faster than they have the mental capacity to safely handle.
The problem I'm finding is that there aren't many helmets around for toddlers. Bike helmets tend to be no good, they can move around too much. I've seen something called a Thudguard, but it looks a bit pants really, just foam. What I'd like is one of those BMX-style helmets, they are a bit more round than traditional cycle helmets, but I can't find one in the smaller size. Any tips?