My wife recently got a child seat made by Giant. Nice quality and came with a rear rack. However, compared to a trailer, I find the seat to be a very dangerous option for carrying a kid. With my 35 lb. 4 year old, the effect on handling was very noticable. I made the mistake of standing up while climbing a small hill at the park and damn near wheelied over. Luckily I got a foot down to keep the bike from falling all the way over. Taking corners felt very iffy at any speed. On the flip side, I"ve carried 2 kids in the trailer with little or no effect other than a little drag while climbing hills.