This video really makes me want to visit Denmark, and maybe take a side trip up to Stockholm and Helsinki. I bet they have cargo bikes there, too. These things remind me of the ubiquitous tuk-tuks of east Asia and the autorickshaws in India. Wholly different types of transportation, so common there that they don’t think twice about it, but so uncommon here in the USA that they’re oddities.
I’m not sure these would work so well in Seattle. Lots of rain plus lots of hills equals soggy kids and groceries spilling out all over the place.