On the eve of hitting the big 6-0 on Feb. 2, Brinkley celebrates her birthday – and her incredible figure! – by posing in a swimsuit on the cover of this week's PEOPLE.
"I'm actually excited about turning 60," Brinkley tells PEOPLE. "I feel on top of my game."
But not game enough to wear a bikini. "My kids would be so embarrassed!" she says. "In private I may wear a bikini, but at the public beach with my kids I would change bathing suits because they do not want to be hanging out with some old broad in a bikini."
Others disagree. "She looks phenomenal," says MJ Day, senior editor for Sports Illustrated's swimsuit issue (Sports Illustrated is a sister publication of PEOPLE). "She has the legs of a 30-year-old and the face of an angel. She's what you aspire to look like at 60. She's mind-blowingly beautiful."
In this week's issue, Brinkley spells out all of her stay-young secrets, from her daily diet to all the beauty tricks to looking half her age.
But after four divorces, including an explosive public divorce trial with architect Peter Cook in 2008, Brinkley credits her three kids – musician Alexa Ray Joel, 28, college freshman Jack Brinkley-Cook, 18, and up-and-coming model Sailor Brinkley-Cook, 15 – as her fountain of youth and her motivation to focus on a healthy lifestyle.
"Because I'm an older mom, I have a responsibility to my kids as well as myself," she says. "I want to be there for them."
For more about Brinkley's diet and fitness regimen, and how she really feels about dating again, pick up this week's issue of PEOPLE, on newsstands now
Plus, catch up with Brinkley and all of Sports Illustrated's most popular swimsuit cover girls on Sports Illustrated Swimsuit: 50 Years of Beautiful on NBC, Monday, Feb. 3, at 9 p.m. ET/PT.