After trying a trailer, backpack, and rear seat, I think the bakfiets is the best way to transport children. Although there are some concerns...(see step 6 for some ideas on the safer ways of placing children in the box).
This instructable is all about how to design and build a bakfiets style cargo bike. The design tips apply to any bakfiets style cargo bike and there is no need to build it out of bamboo. I like the ride quality and uniqueness of bamboo. However, if I do it all over again I might use steel... Building a bakfiets is like building three normal bikes. The amount of epoxy and sanding seemed to add up. I think my next bike may be fillet brazed steel.
Here is the breakdown:
Cost: $600 (including components - mostly used)
Time Frame: 4 months
Larry vs. Harry Bullit
the dimensions of the bullit
Tom's Cargo Bikes
Bamboo Bike Blog
Sources for materials:
Epoxy: West Marine (I used West Systems but I think I should have tried this: http://www.entropyresins.com/products/super-sap-clr - half the price of West System 105)
Bamboo: local bamboo nursery
Drop Outs and Tube: Nova Cycle Supply : http://www.cycle-frames.com/bicycle-frame-tubing/home.php
The art of building bamboo bikes has really come a long way. I have realized that my technique from 2008 is probably not worth emulating. I strongly recommend that you look at the Bamboo Bike Blog and other instructables for the next level of building with bamboo. I particularly like this instructable by kentdvm:
So let's get started!