I'm looking for options for carrying 2 children on the back I'm looking at the Yuba Mundo with 2 Bobike Junior seats to carry my 4 and 6 year old children.  

First, does anybody know if those seats will mount on a Mundo?  

Second, I'm open to all other recommendations, but would like to keep the cost under $2k, so I think that rules out the WorkCycles Fr8 and any bakfiets.  (I've got a Mundo dealer here in Chicago but would consider having a bike shipped).

thanks!
Maybe you'd be interested in a moederfiets (dutch for "mother's bike).

This page appears to be selling them:
http://www.tmannetje.nl/index.htm?errors/404.htm~mainFrame