The kids of home design reality TV series Fixer Upper are growing up fast. Joanna Gaines’ oldest daughter Ella turns 18 years old on Sunday (Oct. 20), and the night before her birthday, the TV personality shared a peek at all the decorations the family set up for the festivities. The Gaines planned a fittingly grown-up birthday celebration for their newly-minted adult, including a blue and sage-green color palette and an international flair. Ella’s birthday spread includes party plates that read “Oui” and a present that includes a book titled Paris Style. It wouldn’t be a party without some cl…