The 58-year-old actor and his model wife Emma Heming welcomed baby daughter Mabel last year, the actor's fourth child.
Willis said of his work: "I'm fortunate in that I get to bring my family with me when I travel. And it would be impossible, impossibly unbearable for anyone I was working with if I didn't have my family with me. I would just be moaning about that."
He joined co-stars Helen Mirren and Mary-Louise Parker for a trip on the River Thames yesterday to launch action comedy sequel Red 2, ahead of the UK premiere. The film is about a team of retired assassins and boasts an all-star cast including Anthony Hopkins, Catherine Zeta Jones and John Malkovich.