Jon decided that he wanted to swap multiple people, not just two. He also decided to have the swap happen every day, just to make it more interesting.
"I wish that for the next seven days, once every day my whole family's personalities would be the same as one family member, and it would change every day"
(every day His whole family will have the personalities of one member, Jon, His Mom, His Dad, Zoe (goth little sister), Becky (older girly sister), Mikey (younger brother), and Sally (Younger sister and Mikey's twin sister) and it changes every day.)