Why do the kids take the bus? Because, their parents feel that is too dangerous to let them walk or cycle, that is why we need 20mph limits, as they do in many other countries on the mainland of Europe. Then we might get away from having the fattest, most miserable, children in Europe...
As an adult, I am used to mixing it with the traffic, but even so I would welcome the introduction of a 20mph limit as this would mean that drivers would have more time to look about them on busy roads. Most accidents crashes on urban roads are because drivers can't cope with the information flow in the busy urban environment at speeds of up to 30 mph (or more). Lower speed limits make it safer and more pleasant for everyone.