Families who have two or more vehicles could easily use only one, with one or more family members biking, walking, taking public transportation, or driving a moped or motorcycle to work every weekday. Even people who do maintain a car just for themselves could take alternate transportation on the weekdays, and use the car only on the weekends.
Honolulu is pretty high up on the list of healthy US cities, and not everyone is a gas-guzzling, tree-killing pig. When I walk to work at the right time of day, I do see plenty of other people walking and biking downtown. I even see some of them transporting their kids on bikes. One Chinese man has a half-grown daughter who sits sideways on the luggage rack, the one over the back tire, and balances perfectly as he speeds down the hill on the way to her school. One dude I saw a couple years ago had a fancy covered trailer rigged up on the back of his bike for his toddler, and another guy had a tandem bike for himself and his son.
But we can do SO much better! If there is enough demand, the city will do something about making the roads safer for bicycles. In a city with nearly perfect weather and relatively short distances to everywhere, we could also cut our demand for gas in half - or more - without even causing ourselves any pain. With that kind of surplus, prices of gas would be sure to go down - if everyone were to participate.