We have just one kid at the mo', but planning another, and we've tried a few things
Croozer 737 trailer - hard to fault the trailer. I guess the floor could do with more waterproofing, but that's about it. Oh, and storage is a pain compare to the Chariot. Other than that, brilliant. Downside was that my son got bored with nobody to speak to, and the risk of stones flicking up meant keeping the net down, so he got really hot when it was sunny. Also, mrs mekon never got over the fear someone would run into the back of him.
WeeRide kangaroo Seat. Easy to fit, and good for child interaction. I never got over the fear that I was using him as an airbag, and he grew out of the seat really quickly. Also, when he messed around, the high CoG played havoc with the steering, meaning close passes from cars were terrifying.
Bakfietsen. Has two, a bakfiets.nl and a defietsfabriek 995 - sold the 995 this weekend. Been brilliant. Within the limits of it's dutch bike geometry, neither have put a foot wrong, If you live in a congested town, I'd suggest a car is a poor alternative to a bakfiets. I am off out with my boy this morning, chucking him and his likeabike in the front and heading off to the park. It usually ends like this...
I've test ridden a Winther kangaroo and a gazelle cabby too. Kangaroo wasn't for me - I found the rear wheel steering effect unpleasant. The cabby was great for the money, If they'd kept it under a grand so C2W peeps could get it for £600, it'd have amazing. Sadly, it's up to £1300 now. Still worth a look.