What helped me immensely was taking some thick petroleum lubricant and a soft brush and lubing every pivot point on the seats (especially the second and third row), doors, hatches, etc. I have found specifically that keeping the rubber ‘bumpers’ where the rear hatch hits the body lubricated makes a big difference in squeaks and rattles.
Also look for dumb things like loose change rattling around under the seats. I spent considerable time troubleshooting a repetitive rattle to discover that a penny had crept into the stereo amplifier housing under the passenger seat.
Good luck!