Christina Ricci on Her New Life as a Mom: 'I Want to Succeed' for My Son Freddie

"Having a child changed everything," the actress exclusively reveals to PEOPLE

Christina Ricci has wowed a generation with her films — Casper, The Addams Family, Now and Then and Monster, to name a few — but these days the actress is focused on entertaining one audience member: her son Freddie.

Ricci, 36, and husband James Heerdegen welcomed their little boy in August 2014.

“Having a child changed everything,” Ricci, 36, told PEOPLE at The Sound Lab presented by Audi at New York City’s Whitney Museum of American Art on Wednesday. “It’s made everything in my life actually important and matter. I now have to take things seriously, and I never did before.”

She adds: “I want to succeed for him. My choices matter more.”

At 19 months, Freddie is already cracking his parents up. “When he’s frustrated, he [shakes his hands] like this,” shares Ricci.

Then there’s his fascination with a particular accessory. “He’s obsessed with hats, so he tries to put everything on his head,” Ricci quips. “And he says, ‘Hat,’ while he does it.”

The event found the star — in addition to museum guests — playing composer in the interactive music exhibit, which Animal Collective created using noises by Audi’s vehicles. For the couple, nights like this have become rare, the art lover says.

“Most of my social things are play dates now,” reveals Ricci. “I barely ever go out at night unless it’s work related. It’s all lunches.”

So what’s her secret to managing motherhood amidst the hustle and bustle of the Big Apple?

Having a “really good” and “not hideous, but also diaper-appropriate” bag for “all the wipes, bottles and the snacks,” she says. “My son really enjoys a good snack — or two or three.”

Just don’t expect Ricci to already start taking on projects to amuse her little man: “I don’t know who he’s going to be yet,” she explains.

Next up for the Golden Globe-nominated actress: Mothers and Daughters, which hits theaters in May. The film’s star-studded cast — including Sharon Stone, Susan Sarandon and Selma Blair — captures the perspective of mothers in interwoven stories.

While discussing the scenes she shares with Courteney Cox, Ricci beams and tells PEOPLE, “It was very exciting because I’m a huge Friends fan and I love her. It was so great.”

— Nick Maslow