Advice on Tagalong Trailer

Hey ladies--I am a newbie to this board. I am looking for some input here about a bike tagalong/trailer/whatever-the-heck-you-call-those-things. I want to be able to pull my 4.5 year old on the back of my bike--so that we can keep up with my 7 year old. I am currently hauling him around in a Burley Trailer--but he is absolutely dead weight--and it is no fun for either of us anymore. I would like to get one of those tagalong bikes--so that he can get a feel for riding (we recently removed his training wheels on his solo bike--and it isn't going so well). Anyway, any recommendations for trailers? I am leaning towards the Burley Piccolo--but it is expensive and there aren't any around that I can test ride. I am pretty petite 5 feet and 105 pounds--so I need to be able to pull him on something that I can control easily. I want something nimble, safe, reliable, and sturdy--that will work on my very small (and old) Bridgestone MTB. I have a new road bike--a Serotta (yay!) but there is no way I am hitching anything to my baby Sir otter! Any advice is most welcome. Thanks!

I will be using this rig mostly on the road--taking him to preschool, grocery store, bike rides, etc.....all on the road.

We used one of those until we graduated to the tandem. It works fine, but can be unwieldy. You sound very petite. I am not. I didn't have too much trouble making the trailer and bike do what I wanted, but I could see a time as your child gets larger that the trailer/kid combo might outweigh you, or at least come close to your weight. I was riding on trails as well as roads, though - if you stick to roads it should be okay. I mostly noticed some lean as the bike was turning. There is just some awkwardness to the trailer that you need to get used to.

You should definitely be able to do it, but it would sure be nice if a bike store would let you test ride on. And yes - definitely put on your MTB and not your road bike!!!