The flight was part of a private holiday tour with four adults and two children in the aircraft. The pilot was conducting an approach to land at a property airstrip. There was a headwing of about 20 kts on final approach and he was maintaining an airspeed of 80 kts. When the aircraft descended below the tree line just before landing it entered an area of windshear. The pilot noted an increase in speed at this time and said that the aircraft bounced a number of times after the initial touchdown. He then elected to go around, applied full engine power, and retracted the flaps from 30 to 20 degrees. He then became concerned about clearing trees to the left of the strip as the aircraft had veered left during the go-around. The aircraft subsequently collided with the trees and impacted the ground heavily. The pilot and one passenger sustained minor injuries. There was no reported problem with the engine or the aircraft during the go-around. Post-accident examination of the aircraft indicated that, at impact, the flaps were in the process of retracting, and the landing gear was down.