DD is 11 months - we have a Kettler Flipper seat on the back of a bike - a Jamis Coda bought specially to tote her around.

The helmet thing is an issue. I can't seem to find a helmet small enough to fit her. I found a really small one through REI (smallest I could find!) and it still falls over her face. So (eek) we ride without it for now. I feel like a bad parent but I am confident we're going to be fine.

She loves it. Please don't flame me.