Note that David is riding a Cruzbike Sofrider (version V2). For pannier racks, he’s using Axiom front racks custom-attached to his bike. Since the current version of the Sofrider doesn’t readily take underseat racks, that seems to be the best solution.
Julie rides a Cruzbike Quest. Photos (buried in the blog) show it fitted with racks and bags.
All in all, an inspiring bit of “keeping it simple” and “Doing It Yourself” and “just getting out and seeing the world.”