Prince Albert of Monaco Shares His Unexpected 65th Birthday Plans (Hint: His Kids Are Kidnapping Him!)

A. Bastello/ Courtesy The Prince's Palace Prince Albert of Monaco

Prince Albert of Monaco and his family are taking an unconventional approach to celebrating his 65th birthday.

Prince Albert was tipped off on how his wife, Princess Charlene, and their children, 8-year-old twins Prince Jacques and Princess Gabriella, plan to celebrate his birthday.

"It's going to be very subdued. We'll have a little family lunch on Tuesday. Afterward, when the children return from school, I'm going to be kidnapped," he tells PEOPLE exclusively. "Really. I've been told to be available to be kidnapped. At 5:30."

"It's a secret. The kids want to kidnap me," Prince Albert smiles. "They want to take me to a play at a theatre, but actually, I've only been warned I'm going to be kidnapped."

RELATED: Prince Albert of Monaco Talks About Friendship with King Charles — and Looking Forward to His Coronation

The family celebration will continue the following day when they attend a St. Patrick's Day concert at the Princess Grace Irish Library in Monaco before Prince Albert heads to Ireland for the formal dedication of "a new statue of my mother in County Mayo."

The informal spirit of Prince Albert's 65th birthday and achieving an age when many are contemplating slowing down isn't lost on him. He downplays the significance of the number, saying with a laugh, "It's only really important in that I see friends, who are the same age, retiring now. I can't do that."

"I mean, 65 is important, but it isn't. I prefer decimals, so 60 was important, 70 will be important. And hopefully, I'll reach 80 and 90 and beyond. Sixty-five has some resonance, I suppose, but for me, it's just another birthday. It's not a milestone. I've said before that 60 was the new 40," he laughs. "And so it continues incrementally — 65 is the new 45!"

A. Bastello/ Courtesy The Prince's Palace Prince Albert of Monaco

Walking a visitor around the continuing renovations and renewal work which scaffolds much of the palace throne room and reception areas, Prince Albert smiles, saying he doesn't "want too many gifts."

"People think this palace is big, but our storage is full," he tells PEOPLE. "I'm serious...I don't know where to put things anymore."

A. Bastello/ Courtesy The Prince's Palace Prince Albert of Monaco

Asked to name the proudest achievement of his 18-year reign, Prince Albert smiles warmly. "You mean aside from my wife and my children? Because they are."

Having previously described his daughter Princess Gabriella as a "pistol," Albert says she still "has that little mischievous twinkle in her eye. She has her own little personality and sometimes does things that are, you know — she'll try to use her brother and get him into trouble..."

"But Jacques stands up to her now, and when he's had enough, says 'No!' So he's not squashed by her strong personality," the father explains.

Both children have been joining their parents more at public events. Gabriella, Albert notes, "can sometimes feel a little uncomfortable around too many people. I see it. Between them now, Jacques talks more, engages more, in public."

The royal adds, "The fact they have normal school activities again, school sports, aren't in the little palace school room and are interacting with numbers of other kids has given them back a lot of confidence. Character develops in different situations, and different experiences bring out different qualities in them."

SEBASTIEN NOGIER/POOL/AFP via Getty Prince Jacques, Princess Charlene, Princess Gabriella and Prince Albert of Monaco

RELATED: Monaco's Prince Jacques and Princess Gabriella Provide Aid to Marine Wildlife on Their 8th Birthday

As a longstanding environmentalist, Prince Albert is keen to pass these qualities on to his children.

"It's that relationship with nature, I believe, which is the first important step — and they've gotten that because they've spent a lot of time at the Roc Agel property, and then we've been out on different boat trips so they understand the natural world, both terrestrial and marine life," Albert explains. "They have that connection. So then you try and show them there are problems. And that's why I've taken them on different events like World Cleanup Day, and they also learn that at school. It's by little steps, that you transmit the ideas of not only of caring for the environment but making certain you don't have too much impact on it."

A. Bastello/ Courtesy The Prince's Palace Prince Albert of Monaco

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!

He adds, "You don't sit them down in a classroom situation but do it as you go along."