Prince George, Princess Charlotte and Prince Louis Join Kate and Prince William at Coronation Rehearsal

The Prince and Princess of Wales, along with their children, were with King Charles and Queen Camilla at Westminster Abbey just days ahead of the crowning ceremony

Coronation rehearsals are in full swing —with Kate Middleton, Prince William and their three children joining in the action.

With King Charles and Queen Camilla's coronation just three days away, the Prince and Princess of Wales brought Prince George, Princess Charlotte and Prince Louis to Westminster Abbey on Wednesday morning for a rehearsal.

They joined King Charles and Queen Camilla as well as the monarch's sister, Princess Anne, for the practice.

On Wednesday morning, King Charles was pictured arriving at Westminster Abbey, where around midday on Saturday he will be crowned by Justin Welby, the Archbishop of Canterbury.

Related:King Charles' Coronation: All Your Burning Questions About the Crowning Ceremony Answered

As the Wales family pulled up into Dean's Yard behind Westminster Abbey, their arrival coincided with a changeover of classes at neighboring Westminster School. When the kids who spilled out into the area to move between lessons spotted the young family, they excitedly waved. Princess Charlotte, who celebrated her 8th birthday on Tuesday (which the family marked with the release of two new portraits), waved back.

Princess Kate seemed relaxed and happy, a bystander says.

Earlier when he arrived, King Charles was at ease with just a few days to go to his crowning. "He was smiling broadly," says a witness.

The arrivals to the coronation rehearsal started with Prime Minister Rishi Sunak. Princess Anne arrived next, followed by Queen Camilla then King Charles (the royal couple arrived separately). The Wales family was the last bunch to arrive.

Both Prince William, 40, and Prince George, 9, will part special roles in the crowning ceremony on Saturday. Soon after King Charles is crowned, the Prince of Wales will kneel before his father and pledge allegiance by saying, "I, William, Prince of Wales, pledge my loyalty to you and faith and truth I will bear unto you, as your liege man of life and limb. So help me God."

Meanwhile, Prince George will be one of King Charles' four Pages of Honor at the event. George's participation at the coronation will make history — according to The Telegraph, the second in line to the throne will become the youngest future king to play an official role at a coronation.

Following the coronation service, Prince George is expected to ride in a horse-drawn carriage as part of the Coronation Procession back to Buckingham Palace with siblings Princess Charlotte, 8, and Prince Louis, 5.

The trial run at Westminster Abbey comes after a meticulous run-through by thousands of troops, including a nighttime procession overnight. A vast procession of hundreds of soldiers — and the Diamond Jubilee State Coach and Gold State Coach — marched down the Mall along with comrades on horseback, just after 12:20 a.m. local time on Wednesday.

Preparations have also been underway in the ballroom at Buckingham Palace, where a "coronation theater" was constructed to mimic the area below the High Altar at Westminster Abbey so those taking part can see the layout and rehearse in private.

Related:How Prince George Will Make History at His Grandfather King Charles' Coronation

Last week, Westminster Abbey was closed to visitors so that arrangements can be made.

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

Earlier, U.K. Prime Minister Rishi Sunak was spotted going into the historic church.

Over the next few days, other practice runs will happen, as one aide at Buckingham Palace likened it to a school play where different parts were rehearsed by different sections.

For more People news, make sure to sign up for our newsletter!

Read the original article on People.