I find a two wheel trailer works very well. The best thing is that, other than a loss in speed and reduced acceleration/deceleration, the bike handles just like it does unloaded. I would never have learned this but with the children to tow a two wheeled trailer became a necessity. It turns out the wider wheel track is a non-issue for me even though this is what I was most concerned with at first.

It's pretty straight forward to build you own. I made one out of an old Rubbermaid "Action Packer" and a couple of Yakima jogger wheels I got on Ebay for $15. Waterproof, huge capacity, easy to load, and makes a handy table at the campsite. If anyone's interested I could post pics and plans. Maybe not the most fashionable...