An overworked Bob Munro (Robin Williams
), his wife Jamie (Cheryl Hines
), their 15-year-old daughter Cassie (Joanna "JoJo" Levesque) and 12-year-old son Carl (Josh Hutcherson
) are in desperate need of some quality time together. After promising to take them on a family vacation in Hawaii, Bob abruptly changes plans without telling them. Instead of a week in a tropical paradise, they're going on a road trip to Colorado in a recreational vehicle.
Dragging his wife and kids kicking and screaming into the RV, Bob's togetherness plan (which is partly a ruse to keep him from losing his job) almost immediately hits a major speed bump. Everything that can go wrong, does. Bob's lame attempts to navigate the unwieldy, oversized vehicle are met with silence and scorn from his resentful family. The RV life is a far cry from their comfortable life in Los Angeles, and every attempt Bob makes to get them into the spirit of the vacation threatens to tear them further apart.
At an RV camp, the Munro family is befriended by the Gornicke family -- an irritatingly endearing happy-go-lucky clan of full-time RVers. The more they try to elude the Gornickes, the more their paths seem destined to cross. But adversity has a way of uniting even the most dysfunctional family members and each setback the Munros experience inadvertently helps them become a true family again.