The civil wedding service for Pierre Casiraghi and Beatrice Borromeo in Monaco – followed by a religious ceremony one week later on the Borromeo family islands in northern Italy – will be held on Saturday in the Pink Palace's Salon des Glaces, the formal gold-leafed reception room reserved for the reigning sovereign's official family functions.
The service will start at 11:30 before 70 family members and friends, PEOPLE has learned, and be officiated by Philippe Narmino, Monaco's Justice Minister. Narmino also conducted the civil service between Prince Albert and Princess Charlene in 2011 and registered the birth of their twins, Prince Jacques and Princess Gabriella.
Princess Charlene and Prince Albert (who discreetly attended Pierre's bachelor party in Spain's Castille Requesens) will be at the civil ceremonies, as will the groom's mother, Albert's sister Princess Caroline, and members of the immediate Borromeo family. Princess Stephanie as well as Pierre's brother Andrea and sister Charlotte are also expected.
The civil ceremony will last approximately 20 minutes, to be followed by a brief toast and a procession down a ceremonial stairwell to the Palace gardens, where the cavagnetu, an informal Monégasque garden picnic, will already be in swing.
Pierre and Beatrice were greatly involved in planning the noon fete, says a source, and have arranged several surprises. Along with roving folklore music and dance groups and the pétanque matches customary to Mediterranean summer afternoons, they've requested their expected 500-plus guests honor an usual dress code: wearing their native regional costume. (Think kilts for those hailing from Scotland!)
"It's supposed to be very relaxed, and they want you to be comfortable," one invitee tells PEOPLE, adding that the groom (who'll change into his party clothes following the civil service) plans to attend dressed as a horseman from France's Camargue marshes.
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As a gift to the couple, the Garde Monégasque will be operating a fairgrounds-style shooting gallery in the gardens and arranging sharpshooter demonstrations. There'll also be a Mât de Cocagne, a traditional pole-climbing contest that has been a Mediterranean crowd-pleaser for more than 500 years.
Following the party, the newlyweds – as well as Princess Caroline, Prince Albert and Princess Charlene – are expected to arrive by 8:30 p.m. at the Sporting Club for Monaco's annual Red Cross Ball, where Sting is this year's featured performer. The show, and the couple's wedding day, will conclude with a breathtaking fireworks display.
Reflecting their international background, the couple have reportedly established three separate gift registers – in Monaco, Milan and one benefitting charity.
The first, at Monaco's shop Czarina, is "mostly antiques, furniture and home furnishings," says one familiar with it. The couple have also informed guests that donations may be sent directly to AMADE, the international children's charity established by Albert's late mother, Princess Grace.
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