We had a Giro helmet for our dd...the backs are flat on most baby sizes to help eliminate pushing the head forward. The trailer (I have an In Step) has the helmet pocket, but at 11 months when she first started riding, she wasn't tall enough for her head to hit the pocket. We put folded towels under her and it seemed to work. You definitely need to start slowly with a very little one as their neck muscles are going to need to get used to holding a helmet. My dd seemed to hold it up ok as long as she didn't lean over...she wasn't able to pull her head back up! Then she was ticked off! But in no time, she was plenty used to it and usually fell asleep.

Now at 3, she "reads" books or looks at scenary and doesn't usually fall asleep. I just put a snack and cup in with her and she's good to go. I pull her only with my hybrid and stick to my neighborhood and the nearby bike trails. It's fun to have her talking to me now instead of screaming.

Have fun!