We have the Chariot bike trailer (made in Canada), but my aunt did all the shopping around for me and picked the trailer up. She liked it because it was very sturdy and had good safety ratings. It has a 5-point harness for the child and can fold down fairly small. We have the double trailer, and my girls (3 and 1) enjoy riding in it (when they aren't elbowing each other).
It comes with a hand-brake if you are using it as a stroller and you can get either stroller wheels or a jogging wheel for it (we liked the multi-purpose use of that). We have the jogging wheel, to make it easier for use on rural roads if we are walking.
It hitches up VERY easily and you can get an extra hitch attachment so that you can put one on both your bike and your husband's to easily take turns pulling the trailer. I don't think you can put a car seat into the trailer - it's too small for that. However, the trailer is very sturdy and the harness holds the child well. I actually managed to wipe out on my bike the first time I was riding with the trailer. I took a corner too fast and I went down, but the trailer stayed on its wheels and the girls were fine. (My 3-year-old now tells me, "Be careful going down the hill, Mommy!" every time we go down a hill.)
Helmets were a bit of an issue. It took us quite a while to find a helmet small enough to fit my 1-year-old daughter. They do exist, so look around for them. We found them at Mountain Equipment Co-op and Walmart. Do look for a helmet that sits very snugly on the child's head. Some helmets have an extra adjustment piece or elastics at the back to hold the helmet in place (it's hard to describe). My 3-year-old's helmet just has the usual two straps that form a triangle from the helmet down under her chin, and it slides around on her head quite a bit. I'm tempted to get rid of it and get another helmet similar to my younger daughter's, that has the extra support at the back of the head so that the helmet stays in place on her head even when it's not buckled up.
The helmets aren't terribly comfortable in the trailer (sitting there kind of pushes it forward on the girl's heads) but they have gotten used to wearing them. It helped that my older daughter wears it to ride her trike or runner bike, so my younger daughter thought it was a cool "hat" and went through a stage of wanting to wear her helmet just for fun. We let her do that, so when she gets to put it on the trailer, it's still "cool."
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