We're taking our family vacation to San Diego for the first time this spring. We'll be getting an airbnb in downtown historic San Diego, it'll be myself, my husband and our 2 year old. First question is, is it imperative to rent a car? We are very go with the flow people and the only thing we really want to make sure we do is the zoo, other than that we have no problemo just staying near our airbnb. Secondly, any must do's, toddler friendly activities, etc ect. TIA!