This is the first year for the service, so Karen has no idea of the numbers it might attract, but is encouraged by the initial response.
"All my friends and family are saying this is going to be big, that they all know someone who will definitely want to come."
The service will include a blessing from Jill and live background music. At its conclusion, attendees are invited to place a flower in a nearby creek in memory of loved ones gone forever. Karen will also hand out lavender ribbons.
"Purple is one of my favourite colours," she says. "That's the reason I picked lavender for the ribbons, as it's a peaceful and soothing colour."
The gathering is an extension of Karen's personal grieving. In the past, her ritual on the anniversary of her sons' deaths included releasing flowers into a body of water and then sitting in the public rose garden beside the Kennedy Park Resort to write poetry.
She will recite three of those pieces at the service.
"My poems are all about expressing what I'm thinking," she says. "They bring me inner peace and give me a good feeling."
Pamphlets will be available for women who could benefit from counselling or being connected to others who've had the same experience. Karen says she dealt with the deaths of her sons in her own way.
"I was married at the time and, with help from my husband and friends and family, I overcame the grieving. But I still cry on every anniversary of my sons' passing. You never get over it.
"It's a hard road — everyone copes with grieving in a different way."
Despite the heartache, Karen says she never thought about not having more children.
"I'm a very persistent person, that's why I'm a believer in 'third time lucky'," she says. "We were told it was at our own risk to have a third child but until you try it, you don't know.
Otherwise, I would have spent the rest of my life thinking what if I had gotten pregnant again. At the end of the day, I've ended up with a beautiful son and daughter. I feel very, very lucky."
Mother's Lament, 3pm, Sunday, May 13, Anderson Park, Auckland Rd end. Info: 021 231 4371.