Katharine McPhee and David Foster Perform Together for the First Time Since Pregnancy News

Katharine McPhee and David Foster have made their first public appearance together since news broke earlier this month that the couple is expecting their first child.

On Saturday, the pregnant Smash actress, 36, and Foster, 70, appeared as part of the Go Gala held by the GO Campaign, which raises funds for orphans and vulnerable children worldwide.

"We're so happy and proud and honored to be a part of the GO campaign," said Foster. "Anything to do with children has got my attention immediately, as well as my wife's."

"You're being a little bit humble," McPhee said, "but David has spent his life creating his own foundation for kids struggling with transplants, so anything to do with children, we are in and you are definitely in because that's what you've devoted your charity life to."

The pair went on to perform Foster's hit "The Prayer," with the Grammy winner playing the piano in the back while the American Idol alum delivered astounding vocals.

Earlier this month, sources confirmed to PEOPLE that McPhee and Foster, who married on June 28, 2019, are expecting their first child together.

On Oct. 6, the couple was spotted in Montecito, California, grabbing lunch together and shopping for baby buys.

McPhee and Foster first met in 2006 when he mentored her and other contestants on season 5 of American Idol.

Foster is already father to daughters Sara, 39, Erin, 38, and Jordan, 34, whom he shares with second wife Rebecca Dyer, and daughters Allison, 50, and Amy, 46, from previous relationships.

Erin previously told PEOPLE that McPhee has been a positive addition to their lives — and they sometimes jokingly refer to her as "Mommy!"

"Interestingly, the age difference has played a role in a positive way," Erin said. "Our dad comes from a generation where women are more passive. He is also passive about his feelings. Kat has really pushed him to open up. We could get into a fight, and then Kat's like, 'No, you have to pick up the phone, call your daughter back.' She's a facilitator, which is really important. She pushes him to be more emotional and more vulnerable."

Foster added that he gives his wife credit for coming "into this" family of five adult daughters.

"I think she navigates it really, really well," he said. "And so do they. Because they could be horrible. It sure makes it easier for me that they get along. It's not a fleeting thing, either. It's been a few years."