With a little prince and princess as guests of honour it was never going to be an ordinary party.
But staff pulled out all the stops today to make Prince George and Princess Charlotte's first official joint engagement a memorable one.
Organisers at Government House in Victoria, British Columbia, brought in a petting zoo, complete with miniature horses, goats and rabbits, and a troupe of children's entertainers to add an extra special touch to the day.
George, three, arrived holding William's hand while his 16-month-old sister was carried in her mother's arm.
The Cambridges, who are on a week-long tour of Canada, were joined at the event by military families.
William and Kate thought the event would be a fun way to introduce the prince and princess to Canadian children.
As soon as the Duchess of Cambridge put her daughter down she toddled off - the first time she has been seen walking in public - and made a beeline for the balloon arch to the petting zoo.
As she hugged the balloons she could be heard to utter her first words in public: "Pop". Charlotte was wearing a pretty smocked blue and coral dress by one of Kate's go-to children's shops, Pepa &Co, costing £74.
George was more hesitant at first, asking for his mummy, but soon got into the swing of things and grabbed an orange, fish-shaped bubble gun which he cheekily fired at his little sister.
Charlotte seemed totally obsessed with the balloons and tried to lift them off the grounds, which made everyone laugh, including her adoring parents.
William asked: "Do you want a balloon Charlotte?" Charlotte could also be heard to call William over, saying "dada". "Yeah," said William turning towards her.
George, meanwhile showed that he had inherited his family's love of anything equine and headed off towards miniature horses Honey and TJ for a ride before
"having a blast" at the bubble station with his father.
Later George could be seen in William's arms looking at a black and white rabbit. But when Kate took Charlotte to have a balloon animal made, George quickly ran over saying:
"But I want one, can I have one?"
Charlotte also spent time petting and bouncing up and down on a six-year-old golden retriever/poodle cross named Moose, who is normally used to comfort adults going through cancer treatment.
The children were also entertained by bubble making machines including giant bubble makers which delighted the military children as they were waiting for the royals to arrive.
There were refreshments on hand in a small tent including fruit juice and paper cups with crowns on as well as tea and coffee for the adults.
There was also a woman dressed up as "Dee Dee" who was created by puppeteer Tim Gosley as public art for the city of Victoria. Tim was entertaining the children with a puppet show accompanied on guitar by Cam Culham, who was dressed in a red and patchwork outfit.
A Kensington Palace spokesman said: "The Duke and Duchess are really pleased to have this opportunity to introduce their children to Canada and it's great that they have the chance to play with other children while they are here."
George and Charlotte have been based with their parents and nanny Maria Borrallo at Government House, the official residence of the Queen's representative in British Columbia.
In anticipation of having two lively young children as guests, child-friendly protectors were plugged into the electrical sockets while staff created a new nursery, complete with toys and teddy bears.
Gardeners even filled the fountains in the gardens with rubber ducks to entertains the young royals.