The Duke and Duchess of Sussex stepped out to the George Zajfen Tennis Tournament, benefitting the Alliance for Children’s Rights, on Saturday, Sept. 14

Prince Harry and Meghan Markle in August 2024. Photo: Eric Charbonneau/Archewell Foundation via Getty

Prince Harry is celebrating his 40th birthday weekend by showing up for a cause that matters.

On Saturday, Sept. 14, the day before his birthday, Harry and wife Meghan Markle made a special appearance at the George Zajfen Tennis Tournament in Los Angeles. The event benefited the Alliance for Children’s Rights in honor of Kelly McKee Zajfen’s late son.

As Zajfen and her family wrote on Instagram on Sunday, Sept 15, Harry and Meghan, 43, showed their support during an “incredible day” that ultimately raised “funds that will go directly to supporting children in foster care, ensuring they have the legal protections, resources and opportunities they deserve in honor of our beautiful son Georgie.”

“To our Presenting Sponsors, The Archewell Foundation. Harry and Meghan, you have been such a guiding light for our family not just in the way you have shown up in friendship but how you have shown up through the incredible work The Archewell Foundation does everyday,” read the Instagram caption from Zajfen, her husband Julian and daughter Lily.

“I’m in awe of your commitment to community and to friendship. On behalf of the Alliance for Children’s Rights, we thank you,” the caption continued. “On behalf of our family, we love you. Extra special day too…HAPPY 40th Birthday H! ✨ May this trip around the sun be the best yet.”

Prince Harry and Meghan Markle attend the 2024 ESPY Awards on July 11, 2024.Kevin Mazur/Getty

Per the event’s website, the tournament featured a round-robin doubles competition and a luncheon to raise funds in support of young people who have experienced foster care. As Zajfen has previously shared, the annual tennis event has been held for more than 20 years, and was recently renamed to honor her son Georgie, who suddenly contracted and died from a viral illness at 9 years old.

The nonprofit itself provides “free legal services and advocacy for caregivers, adoptive parents, and children and teens in L.A.’s foster care system,” Zajfen previously wrote in an essay for PEOPLE.

In photos from the event, which Zajfen later shared on Instagram, the Duke and Duchess of Sussex posed with the Zajfen family — with Prince Harry sporting a white T-shirt and blazer, and Meghan wearing a tan button-up dress. The couple also shared hugs with Zajfen and had conversations with the family on the tennis court.

According to snaps also shared on the Alliance for Children’s Rights and Zajfen’s respective Instagram Stories, Property Brothers star Jonathan Scott, Zooey Deschanel, Zach Braff and Meghan’s friend and former Suits costar Abigail Spencer also showed their support during what Scott called “an incredible event.”

“Our community showed up in a big way and I’m in awe,” Zajfen wrote in her Instagram caption. “Get ready for days of posting images of this magical afternoon because I have so many people to thank and shout from the rooftops just how amazing you all are!”

As PEOPLE previously reported, Harry is marking his 40th birthday weekend with a private celebration in Montecito on Sunday, surrounded by family and friends. The royal family’s social media accounts shared birthday tributes for Harry on Sunday.

“🎂 Wishing The Duke of Sussex a very happy 40th birthday today!” read the post from King Charles’ official account, while Prince William and Kate Middleton shared the King’s post on their Instagram Stories and on X (formerly Twitter), adding the message, “Wishing a Happy 40th Birthday to the Duke of Sussex.”

Harry recently told PEOPLE via his spokesperson, as his milestone birthday approached, that the best gift he has “ever been given is, without doubt, my kids.”

“I enjoy watching them grow every single day and love being their dad,” he said of children Prince Archie, 5, and Princess Lilibet, 3, whom he shares with Meghan.