I will install the car seats and my kids will pepper the backseat with cheerios, fruit snacks and sand box sand. My son will think the car is his new "police car" and crawl around in the front seat pretending to arrest bad guys and test the strength of the center console mount. Windows will be immediately smudged with fingerprints and boogers. That sums up about the first hour. After that one of the rugrats will likely christen the exterior by running a bike into it or smacking it with a broom handle "on accident".
Someone will have the great idea for a family drive to, I don't know, probably Dairy Queen so the kids can cement the Cheerios in place and get to work replacing the new car smell with sour dairy.