Though she spent the early part of the week in Chicago helping Oprah Winfrey celebrate the end of her talk show, Maria Shriver was back in Los Angeles Wednesday, PEOPLE reports. Shriver met two of her children, daughter Katherine, 21, and son Christopher, 13, for lunch at Taiko sushi restaurant in Brentwood.

"She looked relaxed but was a bit pre-occupied during lunch with phone calls and she barely touched her food," an eyewitness told PEOPLE. "She just seemed happy to spend time with her kids over lunch. Their conversation was calm and quiet. They were all smiling and seemed relaxed."

Once they were done eating lunch, Shriver drove Christopher back to school.

The former news reporter announced her separation from husband, Arnold Schwarzenegger, earlier this week--just prior to news breaking that he'd fathered a child out of wedlock.