New mom Liv Tyler is on a mission, and she couldn't be happier.
But in juggling a house move and getting ready to go back to work all while caring for her newborn daughter, the Lord of the Rings actress, 39, admits she has her hands full. "It's a whole new world, juggling four!" Tyler, who is mom to Sailor Gene, 18 months, Milo, 11, and soon-to-be stepmom to her fiance David Gardner's 9-year-old son Gray, tells PEOPLE.
She adds, "This is definitely one where everyone is chipping in. The big boys can hold her, and it's so sweet."
A keen photographer, Tyler has been sharing adorable pictures of Lula and her siblings bonding on Instagram. "With the family stuff, it's tricky. But I feel so proud, and it's so sweet," the new mom says.
Of posting a black-and-white picture of herself breastfeeding Lula two weeks after her birth, she admits, "Honestly, I took that picture for David because we were in bed snuggling and he was at work ... There should be no stigma - it's a very beautiful and natural thing."
Since welcoming Lula five weeks ago, life has been somewhat of a juggling act for the family.
"It's like when it rains, it pours," jokes Tyler, who launched her debut fashion collection with British brand Belstaff on Aug. 1. She's also due to relocate the family to London any day now, where Milo will start school in September - not to mention fly to Australia in a few weeks to film the third and final season of The Leftovers.
Luckily, she has the help of her oldest son, whose dad, British rocker Royston Langdon, the actress and daughter of Aerosmith frontman Steven Tyler split from in 2008. "[Milo] was so helpful when I was pregnant, and he's just the sweetest," Tyler shares. "The age gap is great because he's so responsible, and so is Gray, David's son. They help us take care of Sailor and the baby. They love to hold her and snuggle her, it's very sweet."
And while Sailor is equally smitten, he needs more of a watchful eye. "We're just trying to keep [Lula] alive!" she says with a laugh, revealing, "He wants to pull on her little bassinet. I have to watch him so closely, but he says 'baabyyy' - one of his first clear words, which is cute."
Tyler might be a busy mama, but she wouldn't have it any other way. "I'm completely blissed out. Sitting with all the children and David, I literally keep pinching myself, going, 'Am I dreaming? This is amazing.' "