The moment Zoe drove the car up the Meadows' driveway was probably one of the biggest reliefs of her life. She always thought that driving would be easy, that she didn't need a license to do it, but she found out that that wasn't true at all. She decided that when she got back to normal, she'd wait until she got her license.
After getting out of the car, Jon and his "new" family walked up to the mostly unfamiliar house. They had all seen the house before while passing by on the road, but they had never seen the inside. All the secrets of the Meadows family would be exposed to them.
As they walked inside, Jon realized that if they were staying at the Meadows' house, then the Meadows family would be staying at his house. Because it wasn't just a transfer. It was a swap. Biff was in his body now, living his life.
And Jon had a secret greater than anyone else. And that, of course, was the wishing stone, which he left in his bedroom before he left the house to go on this "retreat". It was still there now.
But how would he be able to get it back? If he even approached his house, that would be a violation of the rules.
But he had to get it back somehow. He didn't intend on leaving it in the hands of someone like Biff.