1. When everybody is walking outside, instead of transiting through cars, it is a lot harder for pedestrians to be robbed. Also, police actually start caring more about pedestrian safety when so many people are walking. Walkable neighbourhoods can be a lot safer than the safest car-friendly neighbourhoods, with the right system.
2. As for carrying, based on my experience of living in a walkable neighbourhood where thousands of people lived within a kilometer of the central shopping area, a lot of people would bring carts that they would push their groceries home in. If you can push a small wheeled grocery cart through the total 100 meter aisles of the grocery store, then you can push a big wheeled cart the 1000 meter to your house on the sidewalk. Given that I often saw 80 year olds doing that, most healthy people should also be able to do it, no problem.