05/05/2013 at 06:00 PM EDT
already knows what she's getting for Mother's Day
this year: a round of applause and, most likely, a standing ovation.
(Melanie, 25, Jillian, 23, Devin, 20, and Sasha, 13) is marking the holiday from her spot on stage
in Broadway's The Trip to Bountiful
. "I have a 3 o'clock matinee. No rest for the weary," Williams, 50, tells PEOPLE, adding, "Maybe my kids will surprise me with a dinner afterward."
Beyond the theater, she's also taking time to honor her late grandmothers, who both died after struggling with heart disease. (Her maternal grandmother died at 64 after having a massive heart attack, and her paternal grandmother died at 28.)
And that's why she's partnered with Bayer Aspirin on its Handbags & Hearts
campaign in the hopes of helping women understand the signs and symptoms of a heart attack.
"I'm very, very aware of heart health," she says. "I'm very mindful of my diet and exercise, and I think being a woman, you have to be."
She adds: "I'm a mother of four, I just turned 50 this year, and I want to be around for a long time."
For those who aren't mothers quite yet – we're looking at you Duchess of Cambridge
– Williams has a few words of wisdom straight from her own heart.
"Motherhood is one of the greatest gifts and surprises in life," she says. "You always have to be prepared for the unexpected. You have to be able to surrender to whatever situation it is and do the best you can at any moment."
Of mom-to-be Kate
, she adds: "I'm sure she'll be a terrific mom."