Zara Tindall May Miss Easter with King Charles — How She's Spending the Holiday Weekend

Princess Anne's daughter attended last year's Easter mass at St. George's Chapel in Windsor Castle with her husband and daughters

Zara Tindall’s Easter weekend might look a little different this year.

On Friday, Princess Anne’s daughter was spotted in the saddle on the grounds of the Thoresby Park International Eventing Spring Carnival in Newark, Nottinghamshire. The professional equestrian, 42, sported sunglasses as she rode her horse Class Affair in photos published by the Daily Mail. The riding carnival runs until Sunday, so it's possible that Zara might miss the royal family’s traditional Easter church outing despite being part of the holiday event in past years.

Earlier this week, Buckingham Palace confirmed that King Charles, 75, and Queen Camilla, 76, would attend the traditional Easter Mattins Service at St. George's Chapel at Windsor Castle on Sunday. The monarch's doctors have advised that he limit the number of people he comes in contact with during his cancer treatment, and the Easter Mattins Service is expected to be smaller scale than usual.

The King postponed public-facing duties but continued to host small audiences behind the scenes since the diagnosis was publicized in February.

Related: King Charles 'Is Positive' amid Cancer Treatment: His 'Doctors Are Optimistic,' Palace Source Says

Confirmation of the monarch's holiday plans came after it emerged that he hoped to attend church on Easter. A royal source tells PEOPLE that King Charles is "progressing well" in his treatment, and there is an "amplified confidence" in the light of the sophisticated treatment he is receiving.

"He is positive, the doctors are optimistic," the source says.

In a recorded message for the Royal Maundy Service on Thursday, the King expressed "great sadness" that he could not be at the centuries-old pre-Easter tradition. Queen Camilla stepped in his stead at the event at Worcester Cathedral, reportedly becoming the first consort to distribute Maundy money to local pensioners at the ceremony, which parallels Jesus washing the Apostles’ feet at the Last Supper.

Related: Queen Camilla Makes History as She Steps in for King Charles at Royal Easter Tradition

While some members of the royal family may join the King and Queen at St. George’s Chapel on Sunday, Prince William and Kate Middleton won’t be among them. It’s understood that the Prince and Princess of Wales are spending the holiday weekend privately at home with their children Prince George, Princess Charlotte and Prince Louis one week after Princess Kate announced that she has cancer.

In a vulnerable video message released last Friday, the Princess of Wales, 42, shared that she is undergoing "preventative chemotherapy" after tests following her abdominal surgery in January "found cancer had been present." Princess Kate explained that her condition was thought to be non-cancerous when she had surgery and described the diagnosis a "huge shock."

"We hope that you will understand that, as a family, we now need some time, space and privacy while I complete my treatment," Princess Kate said in the message, referring to her young children and husband.

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Last April, the royal family was out in full force for the first Easter of King Charles’ reign. The King and Queen led Princess Anne, Prince Andrew, Prince Edward, Sophie, the Duchess of Edinburgh, Vice Admiral Sir Timothy Laurence and more for the walk into St. George’s Chapel at Windsor Castle.

The event was also attended by Zara and her husband, Mike Tindall, their daughters Mia, 10, and Lena, 5 (soon Lucas, now 3, was likely too young to tag along!) plus Prince William, Princess Kate and their three kids, in what doubled as Prince Louis’ royal Easter debut.

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