Helmet for kids for anything other than wakeboarding or motorcycling? Good luck getting him to wear it when you're not around. I went to the bike shop and bought a name brand bike helmet. Can't remember the brand right now, but it's flat black and the design/brand that all the major freestylers wear. When he picked it out it was evident that he was not going to wear the style I wear when I bike. You know, pointy with lots of airflow... It was $50 or 60 and I told him that if I was going to spend that, he was going to have to wear it; not to mention he had a new black Redline bike to go with it too. He "rocked" it for about 20 mins until he saw that he was the only one wearing a helmet and then it sat on the shelf until he outgrew it. So, it is like new, provides good protection and looks awesome in the garage.
Good luck with the decision. You can lead a horse to the most pristine water in town, but you can't make him drink it.