Continuity mistake: In the first scene, Duncan is sitting to the right side (if we are looking at him) of the back seat of the station wagon. When they are taking the luggage out of the car, there are now bags piled up in the seat on the right side.
Suggested correction: Absolutely no telling how much time has passed between the two scenes. With them being on a road trip, they could have stopped for gas, food, bathroom breaks etc and moved the bags around at any time. Even Duncan could have just done it by himself mid-transit to make a little more room on the floor for his feet.