It's a long leap from lip-locking with Britney Spears and Christina Aguilera at the MTV Video Music Awards, but Madonna has now jumped into the role of demure children's book author, PEOPLE reports from its London bureau.

The former Material Girl, 45, was in the British capital Sunday for the international book launch of her wildly hyped "The English Roses" at an exclusive bar, the Kensington Roof Gardens. Unlike most launches for first-time kiddie authors, the event was star-studded in a fantasyland-inspired setting dotted with human swans on stilts and colorful clouds hanging from the ceiling.

Long before Madonna made her entrance, husband Guy Ritchie, 35, took on domestic duties for the couple's children, Rocco, 3, and Lourdes, 6 (though two babysitters were never far away), sitting on the floor with Rocco as they both enthusiastically painted in sketches of the characters in mommy's book.

Moments later, newly married Madonna gal-pal Stella McCartney dropped to her knees and gave some creative pointers to the aspiring artists. McCartney later had to run off to her own birthday celebration -- with a copy of Madonna's new book in hand.

"I haven't read it yet," she told PEOPLE, pointing to an illustration in the book, "but I am pretty sure that character right there is me."

As no children's book launch would be complete without a reading by the author, Madonna -- looking radiant in a knee-length, flowered-beige silk number with matching shoes -- donned pointed reading glasses and took a seat on a white wrought-iron swing, sandwiched between her children.

Her excerpt dealt with school friends who are jealous of a girl called Binah. During the reading, the 130 children in the audience were alternately enthused and restless -- but none more than Rocco, who changed positions throughout.

"As you can see, my son doesn't like to sit still," Madonna said with a laugh.

Then, true to her spirit as a performer, the author stopped, leaving the kids wanting more -- suggesting that anyone who wanted to find out how the story ends should shell out the approximately $20 for the book.

Meanwhile, in other Madonna news, she tells the London Times magazine that she wants a third child, but, "because of my exercising and this that and the other, I've kind of screwed up my cycle a bit."

Still, she adds, "I'm going to the doctors to make sure I'm okay to have a baby, so wish me luck."