For the moment, at least, William will be doing the school run. It's usually Kate who anonymously joins the rush-hour traffic every morning at the wheel of a Range Rover, driving Prince George the four miles from Kensington Palace to his day school in Battersea.
And as well as four-year-old George, Charlotte — who will be three on May 2 — must be delivered to her nursery just a few hundred yards away from KP, behind the Royal Albert Hall.
With the arrival of a new baby boy, it won't be that long before the school run is even more complicated, according to the Daily Mail.
And Kate will be keen to get back into her routine as soon as possible, listening to poppy Capital Radio over breakfast — just as Princess Diana did when William and Harry were toddlers.
According to a source, Kate and William are "very keen" to make sure George and Charlotte are as involved as possible with their new brother, "hence the dash back to KP" before bedtime last night.
The couple are also determined to keep things as normal as possible for George, as he has just gone back to school for the summer term and they do not want his routine disrupted.
For his part, William is good with the children in the nursery — one quality of his father Prince Charles that Diana acknowledged.
"He adores bath time with the children," says one of William's circle.
The new Prince will be introduced to a surprisingly "normal" life in Apartment 1A at Kensington Palace. While there are domestic staff — with an intriguingly international flavour — they are nothing like the number employed by Charles and Diana when William was a child. They had a least a dozen full-time staff in London, including a dresser for the Princess, housekeeper, butler and a valet for the Prince.
The key figure today is Maria Borrallo, 47, the stern-looking, but engagingly personable, nanny who has been with the couple since the arrival of George.
Nanny Maria, who was known as "Santa" [Spanish for holy or saint] by friends because they thought she might become a nun, lives in at Kensington Palace, where she has her own private quarters of bedroom, sitting room, kitchenette and bathroom.
Born in Madrid, Maria is a familiar figure in her Norland Nanny uniform of beige nurse's dress and little brown bowler hat, marshalling the children at the Round Pond in Kensington Gardens, sometimes taking them to Hyde Park and, inevitably, to Bucklebury Farm Park deer safari, in the Berkshire village where Kate's parents Mike and Carole Middleton live.
Then there's the housekeeper, Antonella Fresolone, who used to be one of the Queen's senior housemaids, working at Buckingham Palace for 13 years. As well as overseeing the running and cleaning of Apartment 1A, she loves serving up steaming pasta dishes from her native Italy to the family.
Fijian ex-paratrooper Tifare Alexander — known as "" — performs odd jobs and the occasional bit of chauffeuring.
When Prince Philip retired from official duties last year, two of his staff who were on secondment from the Army — Corporal Stewart Harvey and Lance-Sergeant Stuart Hayes — moved across to join William and Kate's team as orderlies and, when needed, to help Harry at nearby Nottingham Cottage, which he now shares with fiancée Meghan Markle.
Their duties, apart from walking William and Kate's pet cocker spaniel Lupo, have been to help as waiters at social functions and official dinners, as well as cleaning shoes and delivering hand-written notes, a royal custom.
The new baby will be brought home to a household that is relatively informal by royal standards. William tends to call staff by their first name, rather than their surname as his parents mainly did.
"It's the home of a modern couple, lots of photographs of the children and the bits of artwork they bring home from school," says a friend.
"It's a welcoming home, but William does guard their privacy and he limits the number of outsiders who are let in to the family circle." Evenings are often spent in front of the television with a take-away curry from Malabar in Notting Hill — collected by one of the orderlies, not delivered.
William has succeeded in creating something of the warm family atmosphere he found with the Middletons when he first knew Kate. But, as working royals, he long ago accepted that his and Kate's home could never be quite like theirs. He's matched them in one area, however — like them, he now has three children.
By last night everything had been made ready in the Peter Rabbit-themed nursery to welcome home George and Charlotte's new baby brother. I gather there are some new additions to the nursery, but no fresh licks of paint.
There are, however, lots of new soft toys already — some from George and Charlotte — and many baby presents have also been delivered to the Palace.
Officially, the couple say they won't be hiring a maternity nurse to help with the early days of the new arrival. Insiders say Kate plans to breastfeed her new baby, but no one would think less of her if she did decide to call in specialist help, particularly during the night (a maternity nurse will normally sleep with the newborn and take the baby to its mother to be fed).
After the birth of Prince George in 2013, Kate was on her knees with exhaustion because he hardly slept, and wanted his mother's constant attention.
When George was born, William and Kate had the builders in at Kensington Palace and were still living in cosy two-bedroom Nottingham Cottage.
They almost immediately headed off to the Berkshire home of the Duchess's parents.
By the time Charlotte arrived two years later, the £4.5 million refurbishment of Apartment 1A had been completed. With five reception rooms, three master bedrooms with adjoining dressing rooms and bathrooms, there is certainly plenty of space.
The imaginative transformation includes a night nursery where Charlotte and George sleep, and a day nursery for playtime.
On the first floor are the master bedrooms with en-suite bathrooms, and his-and-hers dressing rooms.
On the top floor, reached by a lift, are nine further bedrooms for staff, while a basement area where the photographer Earl of Snowdon once had his darkroom is now a well-appointed gym with laundry and luggage rooms nearby.
The kitchen, on which the couple spent £170,000 of their own money, is the heart of this royal home, and where they like to entertain close friends and family.
For more formal occasions guests, who arrive through a bright and airy entrance hall with intricate cornicing and black and white flagstones, are shown to one of the two drawing rooms — in one there is a grand piano and cream sofas with floral scatter cushions.
Soon enough, the latest addition to the House of Windsor will no doubt be crawling all over them with mischief in mind.