Prince William, Kate Middleton and Kids Arrive at Coronation Rehearsal

The Royal Family is gearing up for King Charles and Queen Consort Camilla's coronation ... so, the next in line to the throne is front and center with his brood practicing their part in the ceremony.

Prince William and Kate Middleton were at Westminster Abbey Wednesday morning -- with Prince George, Prince Louis, and Princess Charlotte in tow for one of many run-throughs before Saturday's ceremony.

William and 9-year-old George have some big parts to play in this weekend's coronation ... with William pledging allegiance once Charles is crowned by the Archbishop of Canterbury, and George taking on the role of one of the Kings' 4 Pages.

Can't have the kid messing up, so these rehearsals are crucial!

The man and woman of the hour, King Charles and his Queen, were also on hand Wednesday -- apart from them, Charles' sister Anne was in the building, too ... all a part of the not-so top-secret rehearsal.

As we reported, Prince Harry -- despite all the bad blood -- will be attending his father's big day. He was not at the family run-through, and it's unclear how involved he will be in the coronation itself.

Meghan Markle got an invite too, but won't be heading overseas with her hubby.

FYI -- a Buckingham Palace ballroom had reportedly been recently turned into a mock version of the Westminster Abbey location where people have been able to work through the layout and rehearse on a more private scale.