Each race participant is being asked to raise €250 for the charity, with the overall aim of raising half a million euro.
D'Arcy said: "This is an exciting and unique event. Running a half marathon is a brilliant personal achievement; add to that raising €250 for the most deserving charity along with 1,999 other people and you have a very special communal achievement.
"We are asking 2,000 runners to run over 26,000 miles collectively to raise half a million euro for LauraLynn."
Paul O'Sullivan, Head of Marketing, Volkswagen Ireland, said: "We are delighted to support Today FM on such an exciting event for a very worthwhile cause.
"LauraLynn provides a very important service to families when they need it most, and we are honoured to have the opportunity to support them in their work."
Philomena Dunne, CEO of LauraLynn, added: "We are delighted to have the support of Today FM, Volkswagen and Athletics Ireland and we are really looking forward to the day.
"All funds raised will help us to start LauraLynn@Home, a programme which we will be running this summer initially in two locations, to bring hospice care to children in the comfort of their own home."
Each participant must register on the Athletics Ireland website, www.athleticsireland.ie, where they can either pay €250 for immediate registration or register their details and create an online MyCharity page in order to raise €250.
MyCharity will inform Athletics Ireland once the €250 target has been raised and registration will be confirmed.