I've fit a weeks worth of groceries on my bike pretty easily. Between the rear rack, the panniers, and the trailer I can haul a lot of groceries. But you are right that it's a good idea to have at least one car in a family. Especially in the US. Although I would check first that it isn't cheaper to get a rental or a taxi when you need it. The only reason I still have my current car is because it's already paid for anyways and doesn't cost much to keep around.