It seems like speed will be an issue if this is limited to sidewalks. Maybe what's needed is something partway between a car and say a bicycle. I think it needs to move faster than walking speed to be practical in most areas (you mention suburbs but delivery restaurants in suburbs aren't usually within walking distance of very many customers). I would think something more like the speed of a moped or bike would be needed. That means it probably would need to operate on the side of the road most of the time, not on the sidewalk. It would need to be quite narrow not to interfere with traffic. Maybe some sort of tricycle arrangement would be feasible.
As for actually building this you're going to need a team skilled in machine learning, computer vision and robotics and right now I don't think there are many of those around. You say you're looking for skilled engineers but what makes you think you'll be able to attract people with the right skills ?