The War with Grandpa

The War with Grandpa is a movie starring Robert De Niro, Uma Thurman, and Rob Riggle. Upset that he has to share the room he loves with his grandfather, Peter decides to declare war in an attempt to get it back.
Peter is thrilled that his Grandpa is coming to live with his family. That is, until Grandpa moves into Peter's room, forcing him upstairs into the creepy attic. And though he loves his Grandpa, he wants his room back - so he has no choice but to declare war.