Every few years, Robert De Niro likes to mix it up. He’ll throw in “Last Vegas” or “The Intern” to remind us all he’s more than Travis Bickle or Jake LaMotta. He can also be a generic old man with a deep voice and a contract that requires him to wear reading glasses for 70% of the movie. And so arrives “The War With Grandpa,” an adaptation of Robert Kimmel Smith‘s 1984 novel, directed by animation veteran Tim Hill, with a script by Matt Ember and Tom J. Astle.