This to me is such a tough call to make. The bike seat for a child or the trailer, whether to ride with a child at all even. I don't like the bike seat for several reasons. First the seat is loaded when the bike is on 2 wheels and changes the center of gravity while riding. Second, the child is strapped onto the bike as opposed to the rider who sits relatively unattached, so a parent would have to maybe need some help just to load the child into the chair and strap them in. Precious cargo as the payload is a living human being and not a sack of groceries, that while it would be unfortunate to drop a couple liters of soda, it would be more tragic to drop a bike with a child strapped in. Then there's a worst case scenario, I mean someone hits them with a car, the rider probably rolls onto the hood, while the child becomes part of the bike and goes down immediately to the pavement, maybe under the car ? With the trailer, the 2 wheel type, that's if there is even a single wheel trailer for an infant ? I don't know, but I could also envision someone trying to make something like this work for a 1 wheel trailer to modify it to carry a child and later be used for cargo ?

http://www.biketrailershop.com/bob-y...Fcyb7QodhBD8Vg

Anyway, the 2 wheel trailer makes the bike a more stable tricycle to load and unload, but like others pointed out, lower to the road and unseen. I'd definitely restrict riding to a safer neighborhood and park that has cycling paths if I was going to ride with a chid on any bike.