Los Angeles: Actor Robert De Niro-starrer family comedy "The War with Grandpa" is set for release on April 21 next year. Tim Hill will direct the film, based on the 1984 children’s book by Robert Kimmel Smith, in which a boy is forced to move out of his room when his recently widowed grandfather moves in, reports variety.com. With the help of his friends, the boy devises outrageous pranks to make his grandfather surrender the room, but he turns out to be tougher than expected and all-out war ensues. Phillip Glasser, Marvin Peart and Rosa Morris Peart are producing the project with Jane Rosenthal and Barry Welsh serving as executive producers. Lisa Addario and Joey Syracuse wrote the first draft and Matt Ember and Tom Astle are currently doing a polish on the script. Marro Films is financing and producing the movie with Dimension distributing.