And first stop for getting into the spirit of the occasion was a stop at famous Tinseltown market Mr Bones' Pumpkin Patch.
Emma brought the little girl – who was cute in a pink gingham smock and leggings – along to help her pick out the perfect pumpkin.
Mabel seemed fascinated by her surroundings, pointing out good specimens to her 35-year-old model mum. At one point the sweet youngster had a ride in one of the market's shopping carts.
According to Bruce, his daughter is developing a strong character. Emma retweeted one of his comments which gave an insight: "I know who the boss of this family is. She's sleeping in that crib in the other room."
Mabel Ray Willis was born on 1 April 2012 – adding another female to Bruce's family. The little girl has three big sisters, Rumer, 25, Scout, 22, and 19-year-old Tallulah from her dad's marriage to Demi Moore.