The pilot advised that at the time of the incident he was carrying out a last +fly around; of his property which had recently been sold. The pilot's three year old son was the only other passenger on board. While manoeuvring at low level the pilot's attention was diverted into the cockpit for a period of time, assisting his son who had become ill. During this period of distraction the pilot had inadvertently allowed the aircraft to descend. He recalls looking outside the aircraft again just as it impacted the ground. The pilot confirmed that the aircraft's engine and flight controls were operating normally at the time. The pilot received serious injuries to both ankles in the accident. The passenger received only minor cuts and bruising. The aircraft was damaged beyond economical repair.