I was looking for accessories for my new Chariot trailer and I found a bike shop that carries Kettrikes. They're awesome! The videos on their site show the front wheel is able to lock and unlock depending on whether you want to push from behind or let the child steer on their own. The pedals let the child coast with their feet on them and still brake when going backwards.
WoW. Vanessa on a Tricycle seems like so far away. I think she'll be ready before I will.