I love love love the idea of an update/remake of this movie to address a modern mass migration - specifically following desperate Hondurans fleeing their homes to escape violent drug cartels and the political morass that has spiraled out of the US's interference in South American politics (including but not limited to war on drugs). Change Tom Joad to Tomas Rivera and let's go.
That said, are we sure this movie hasn't already BEEN remade? The movie follows a family on road trip towards a goal that might be a mirage but might also save them, it's structured as a series of episodes and incidents along the way that illuminate the themes and characters of the movie, and the family is made up of an ineffectual dad, a loving but maybe underdeveloped mom, a son questioning his place in the world, a wise elder who dies en route, an uncle along for the ride, and a young woman carrying the family's hopes) and I realized - oh shit, is Little Ms. Sunshine the Grapes of Wrath, minus the political content?