Palace Confirms King Charles Will Attend Easter Church Service amid His Cancer Treatment

The update comes after a royal source told PEOPLE the monarch is "progressing well" in his treatment

King Charles is set to step out for a royal holiday tradition: the Easter church service.

On Tuesday, Buckingham Palace confirmed that the King, who is undergoing cancer treatment, and Queen Camilla will attend the traditional Easter Mattins Service at St. George's Chapel at Windsor Castle this Sunday. Other members of the royal family are also expected to attend.

The update on the King's Easter plans came after it emerged that the monarch, 75, was hoping to attend the church service. The event is expected to be smaller-scale than usual, following doctors' advice to limit the number of people King Charles should come in contact with during his treatment.

It's understood that Kate Middleton, Prince William and their children, Prince George, Princess Charlotte and Prince Louis, will not be among the royal ranks following Princess Kate's cancer news announcement on March 22.

Related: Kate Middleton and King Charles Are Both Undergoing Cancer Treatment. Is It Safe for Them to Greet the Public?

Uncertainty swirled around what the royal family's Easter Sunday plans might look like this year. While King Charles has postponed public-facing duties while receiving cancer treatment, Easter (and other holidays like Christmas, complete with royals' walk to church at Sandringham) are technically private family events rather than royal duties.

A royal source tells PEOPLE the monarch 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.

The insider adds that King Charles is planning for a "summer diary" but won’t commit to any engagements to heed “medical advice nearer the time.”

The King's recent outings have been capped at smaller numbers of people, but as summer nears, more engagements could happen outside —  like as Trooping the Color, the annual military parade marking the monarch's official birthday.

"One thing that has been wholly undiminished is his appetite for work," the royal source says about the King's drive.

The King has continued to work behind the scenes while receiving cancer treatment, a diagnosis Buckingham Palace announced on Feb. 5.

Related: Kate Middleton Had Private Lunch with King Charles Before Cancer Announcement: They Have a 'Very Good Bond'

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On Tuesday, he welcomed community faith leaders from around the U.K. to Buckingham Palace to learn more about their experiences participating in the Windsor Trust Leadership program, a charity providing transformational courses for senior leaders.

Interfaith relations have been a lifelong interest for the King, and the meeting of faith leaders fell just a few days before Easter.

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