We have a Bo-bike which is like a wee ride as it sits up front of the bike. The good thing is that you can see your toddler and unlike rear mounted ones they don't have to lean out to see so they don't destabilise the bike. The bad thing is they can ring the bell!!!

We had a trailer but I found it hard to attach and it would drive me crazy. It was also quite heavy but it is great when you have to cart around a lot of stuff like nappy bags, food, etc