I'd mostly second the Christiania recommendation. Good cargo bikes and the guy who started the company is a great guy. And, I very strongly agree with having your kids up front rather than staring at your rump. Much more enjoyable for them and you, makes conversation easier, and they can see stuff a lot better. You can also mount a seat on the top tube of a city bike or stick a bobeke on your handlebars.
Of cargo bike options I'd rank them as:
Workcycles Kr8
Bakfiets.nl
Christiania (2 - wheel)
Christiania trike
Larry vs Harry
Big Dummy
Xtra Cycle
Avoid: Babboe
The Workcycles is the best riding of the bunch especially when you have a load. Bakfiets second and Christiania third but all fairly good. I think construction quality on all three is similar (Babboe is quite awful however). My biggest issue with the Larry vs Harry is that it can be really squirrelly. I think people that own them get use to it but I never did. I've not ridden a CETMA so no idea how it compares.
Personally I'd never get a Big Dummy or Xtra-cycle simply because I strongly prefer having kids up front and because the box bikes can carry a lot more stuff a lot easier.
FWIW, I have a bakfiets and absolutely love it.
Last edited by CrankyOne; 02-02-15 at 06:21 PM.