The Alice Sebold adaptation tells the story of murder victim Susie Salmon, who continues to observe her family on Earth after her death as her killer prepares to strike again.
McIver will play Susie's younger sister Lindsey, while Dando has been cast as outsider Ruth Connors, one of Susie's classmates.
As previously announced, newcomer Saoirse Ronan will play Susie, alongside cast members Rachel Weisz, Susan Sarandon, Ryan Gosling, Stanley Tucci and Michael Imperioli.
'We auditioned all over the world for the characters of Lindsey and Ruth, but in the end we found that the best actor for each role happened to be a young kiwi,' Jackson, who is directing from a screenplay he co-wrote with Philippa Boyens and Fran Walsh, said.
'We're thrilled to be able to work with Rose and Carolyn and think their casting proves the great depth of acting talent that we have here in New Zealand.'
Filming is set to begin in October in Pennsylvania and New Zealand. Paramount will handle worldwide distribution.
Carolynne Cunningham, Jackson, Walsh, and Aimee Peyronnet are producing. Film 4's Tessa Ross serves as executive producer alongside Ken Kamins and Jim Wilson.
McIver has starred in several films for the Disney Channel including Johnny Kapahala: Back On Board and Eddie's Million Dollar Cook Off, as well as New Zealand television series such as Rude Awakenings and Maddigan's Quest.
Dando is a complete newcomer to film.