do you not wear a helmet cause your such a "skilled" that you don't fall? Well you prolly do where a helmet, even on easy rides, so why is that? Well somtimes **** happens and you can't really account for everything, we've all had falls that where unavoidable acts of nature (stick blown into spokes ect) So now you wanna have a kid on the back of you bike ready to be catapulted into the ground?
Get child trailer (burley chariot ect) and use it on the road or very smooth dirt paths (not singletrack)
All the child seats mount via a rack, so a full squish is a no go