General aviation pilot reported a near miss with another aircraft that was flying opposite direction on final while departing at a non-towered airport during a qualification flight. The aircraft on final maneuvered to avoid the departing aircraft.

Narrative

Myself and the pilot flying had been in the traffic pattern; both of us re-establishing currency in the aircraft. I was in the front seat; and he was in the back seat. We were using runway 27; the wind was 270 at 10 - 15 knots. I had made the previous landing and taxied back; then handed off the aircraft to the pilot in the back seat to make the next pattern and landing. An Aircraft Y had made a call on CTAF; 'Aircraft Y... on RNAV 09; circle to land runway 27'. We briefly discussed and agreed that we would expect the Aircraft Y to break off the approach into the downwind. I was aware the pilot in the backseat had no forward visibility; so I was watching for Aircraft Y approaching Runway 9 as we prepared to depart Runway 27. The Aircraft Y made another radio call; 'three mile final on RNAV 09; circle to land runway 27' as we taxied onto the runway. I then made a radio call announcing our departure on runway 27. As we began our takeoff roll; I spotted the approaching Aircraft Y and announced to the pilot flying; 'Aircraft Y in sight'; followed shortly by; 'he is nearly over the runway'. Due to being in the back seat; the pilot flying could not see the aircraft and responded to me; 'take the controls for evasive action if needed.' I did not expect the Aircraft Y to be so close; so low; or to overfly the departure end of runway 27 based on his 'circle to land' announcement. As we broke ground I watched the Aircraft Y; ready to take the controls; and the Aircraft Y broke off the approach; announcing departure to the southwest. The Aircraft Y then asked if we made a departure call; to which I responded our current position and confirmation that we did make a departure call. With the Aircraft Y so close and approaching from the opposite direction; the better choice would have been to have waited to make our departure. There was nothing rushing us. When I spotted the Aircraft Y surprisingly close and low; I should have said; 'abort; abort; abort' and alerted the pilot flying to abort the takeoff (or pulled the throttle myself) rather than simply announcing my observations.