Cargo Bikes

I rode one as postal worker and they handle like an ATV more than a bicycle. Also heavy as hell!
You have to be prepared to lean/countersteer with your body into corners or go very, very slowly.
The design feels more rigid than a Christiania though as the frame doesn't scissor.

We've had two niholas (switched the standard family for an electric 4.0 recently) and we love them.
They understeer like crazy at any kind of speed and it's trivial to pick up the inside wheel (but they're remarkably stable on two wheels) but that only happens when I'm riding it and I've never had it tip (or feel like it's coming close) with kids on board.
The akerman steering takes a bit of getting used to but I much prefer it to a hinged Christiana type box trike. They are pretty heavy but the way the design puts most of the weight over the front wheels means you can pick it up by the saddle and pivot it around much easier than any other trike I've ridden.
They're not particularly fast (even with the motor) but IMHO they're a huge amount of fun

You probably have all the answers you need, and may already know this, but you can rent these in Dulwich park if you're London based and wanted to try them.

[Edit] sorry, read shortly after posting the above that you'd bought one!