I used to drive a Ford Fiesta which is smaller than your car and I could haul 3 adults, a dog and camping gear for these and drive on country roads. For daily carry I had more than 25 kgs on the car.

Your gas tank will not hit the ground.

Also if you intend to carry heavy load in your trunk everyday just change your rear shocks with suitable ones. Should not cost much. If you know basic DIY on cars you can even do it yourself.

Burak