Riding with Daddy

Since the weather has been nice part of the time lately, Brent decided to go ahead and install the child seat on his bicycle a few weeks ago. This afternoon when I got home, the weather was beautiful and Samantah was begging to go outside, so out we went. Then Brent brought out the bicycle and she absolutely loved riding around with him. My only question is, should she be wearing a helmet, and if so, where can we find one small enough?