But her hectic juggling has led to what the jazz artist calls the most blissful time in her life. No longer singularly career-driven, Krall, at 44, said she's finally found the elusive balance between personal and professional.
"I'm just doing better work because I'm more relaxed ---- you don't have too much time to obsesses or worry," Krall said during a recent interview to promote her just-released CD, the bossa nova-inflected "Quiet Nights," inspired by stirring performances she did in Brazil a year ago.
"That's why I like this record so much, because it was so easy and I enjoyed it so much. It's not my only thing," the Grammy-winner said. "I don't know if you can have it all. ... (but) I think I'm living beyond my wildest dreams."
Her longtime producer, Tommy LiPuma, sees a newfound confidence and exuberance in Krall, not only as a person, but as a performer. While he credits that partly to her growing veteran status ---- "There's this overall thing that comes with time and experience" ---- he also sees the enormous impact of her family.
"I'm sure that her life and how positive it's been and what a great relationship (she) and Elvis have ---- and she's got two beautiful boys ---- and all of that I think is great," he said.
Though her onstage persona is cool and sultry, the Canadian-born Krall, who lives in Vancouver with Costello and their two sons, Dexter and Frank, is warm, giggly and gregarious as she stretches out in a swanky hotel in New York City's lower east side.
She shows off photos of her kids from her phone, talks of date nights with Costello, and gushes about President Barack Obama and wife Michelle after her performance recently at the White House for a tribute to Stevie Wonder.
Krall's boys are the focal point now, but she admits to not really attending much to her personal life in the early years of her recording career, when she was transforming from a promising young jazz singer and pianist to a crossover platinum sensation.
In those days, she remained focused on performing, and also caring for her mother, Adella, who was diagnosed with bone cancer, and whose death in 2002 Krall describes as "the worst thing that ever happened to me."
A year later she found a different kind of love with Costello, but credits close friend Elton John with reminding her that the biological clock was ticking.
"He says, 'Diana, you're 39 ---- you're going to be 40. You better start thinking about having kids,' and I went, 'Right ... .' But usually, you'd have a parent, your mom would tell you that," she said.
When children soon followed, "the lights kind of went ---- 'Oh, I feel my mother back in me."'
Krall took her twins on the road for her 2007 tour, and is doing so again for "Quiet Nights." She counts herself among the blessed working mothers, with two nannies, a sister to pitch in and an entire band that has become a second family.
She also gives full credit to the other entertainer in the household.
"We're equal parents. He's home with them now with Vancouver, and he looks after then when I have to go to Washington to play for the president," she said, laughing.