The ferry itself can carry cars, but bringing a car along doesn't add anything unless you intend to continue on to the Olympic Penninsula. Instead, just walk to the ferry terminal and then on to the boat. It's $7.50 for an adult and $6.05 for kids 6-18, but you only pay westbound. The return trip from Bainbridge Island is free on foot (although if you drive, you pay to come back as well). Once you're off the boat, there are two options to get downtown, the first is along the main street and the second is a more scenic route that goes by the water. When you're walking up towards Winslow Way, look for the waterfront trail sign if you'd like to take the scenic path.
Plus, at the very end, we'll even talk a little planner shop about the new "complete street" improvements that were recently completed on Winslow Way to make it more pedestrian friendly (If you're feeling impatient, you can jump to that discussion by clicking here).