I let my 7 year old pick his helmet. He chose the Green Skull Camo. Seems comfortable (even when I put it on although a little snug), but the advantage I like about it is that I can find him anywhere on the mountain because of the color/pattern. He also got a ton of compliments on the sheer coolness and people noticing that his helmet matches his skis.
seem to do the job. No complaints from my 7 year old son. Read a few reviews that they were smaller than they appear, and won't fit the face of anyone older than 3. That was not my experience. Comfortable, no fog so far, although they've only been used once on somewhat of a warm day.