Prince George,Princess CharlotteandPrince Louisare getting in the Christmas spirit.

Before making their way inside, Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5, made an important stop. They walked over to a red mailbox outside Westminster Abbey and placed envelopes inside. This year, children were encouraged to send homemade Christmas cards to other kids who might be struggling this year. According toroyal reporter Rebecca English, George, Charlotte and Louis all wrote their own cards.

Princess Charlotte, Prince Louis and Prince George mail letters to Santa at Christmas concert on Dec. 8, 2023.Chris Jackson/Getty

Princess Charlotte of Wales, Prince Louis of Wales and Prince George of Wales post letters to Santa before The “Together At Christmas” Carol Service at Westminster Abbey on December 08, 2023 in London, England.

Chris Jackson/Getty

Prince Louis then held hands with Prince William and Princess Charlotte held hands with Princess Kate as they headed inside.

While Prince George and Princess Charlotte made their debut at the event last year, Prince Louis joined in the fun for the first time, makinghis debut at the festive night out.

Prince George, Princess Charlotte and Prince Louis attend Christmas concert with parents on Dec. 8, 2023.Chris Jackson/Getty

Kate Middleton princess of Wales Catherine Christmas carols London 12 08 23 william louie george charlotte

After the service, Princess Kate and Prince William with their children followed the clergy in the processional out of Westminster Abbey, all holding lit candles.

Prince George, Princess Charlotte and Prince Louis attend Christmas concert on Dec. 8, 2023.Chris Jackson/Getty

Prince George of Wales, Princess Charlotte of Wales and Prince Louis of Wales attend The “Together At Christmas” Carol Service at Westminster Abbey on December 08, 2023 in London, England.

Prince George and Princess Charlottemade their debutat the holiday event supporting their mom last year. Wearing perfectly coordinating outfits, George, Charlotte, William and Kate headed inside the venue and sat together for the service.

Although all three of Prince William and Princess Kate’s children stayed home when Kate hosted the first event in 2021, they’re now regulars at Christmas events with the royal family. In 2019, Prince George and Princess Charlotte made theirChristmas morning debutalongside the royals for their annual walk to church services — and last year, Prince Louisjoined for the first time!

Prince Louis, Princess Charlotte and Prince George with their parents, Prince William and Kate Middleton, at the Christmas concert on Dec. 8, 2023.Samir Hussein/WireImage

Prince William, Prince of Wales, Prince Louis of Wales, Princess Charlotte of Wales, Prince George of Wales and Catherine, Princess of Wales attend The “Together At Christmas” Carol Service at Westminster Abbey on December 08, 2023 in London, England.

Samir Hussein/WireImage

Can’t get enough of PEOPLE’s Royals coverage?Sign up for our free Royals newsletterto get the latest updates on Kate Middleton, Meghan Markle and more!

The Prince and Princess of Wales' three children are also likely participating inholiday festivities at their new school, Lambook, where they started in September 2022.

According to theschool’s website, “Christmas festivities and opportunities make it even more special for our pupils, with every single child performing in a Christmas event, including Christingles, Nativities, Pre Prep House singing competitions and of course, our end of term Carol Service.”

Earlier this month, Lambrook School started the Christmas season with anAdvent servicecomplete with a choir performance and nativity scene.

Princess Charlotte, Kate Middleton and Prince George at the Christmas concert on Dec. 8, 2023.Chris Jackson/Getty

Princess Charlotte of Wales, Catherine, Princess of Wales and Prince George of Wales attend The “Together At Christmas” Carol Service at Westminster Abbey on December 08, 2023 in London, England. Spearheaded by The Princess of Wales, and supported by The Royal Foundation, the service is a moment to bring people together at Christmas time and recognise those who have gone above and beyond to help others throughout the year.

source: people.com