A seemingly harmless family vacation goes desperately awry when everything that could go wrong does, ultimately leading them to bond with one another in a way they haven't in a long time. If this premise sounds reminiscent of the much-missed "National Lampoon's Vacation" series, it is, but it is also a valid description of the breezy, good-natured "RV." While the comic elements don't always work—some are too broad, slapsticky or predictable to hit the bull's-eye—the film by and large is smarter and more clever than initially expected. Additionally, there is a sweetness in the way the family unit is accurately captured by director Barry Sonnenfeld (2002's "Big Trouble") and screenwriter Geoff Rodkey (saving face after the calamitous recent remake of "The Shaggy Dog"). The kids might be growing up and the whole of the family might not be as tight-knit as they once were, but there is still love there, and a desire to stick up for each other when the chips are down.

Missing the days when his children still needed and looked up to him, workaholic father Bob Munro (Robin Williams) cancels the family's planned Hawaiian vacation at the last second after getting the idea of renting an RV and driving cross country to the Colorado Rockies. Bob actually has an ulterior motive he doesn't want wife Jamie (Cheryl Hines), 15-year-old daughter Cassie (Joanna 'JoJo' Levesque) and 12-year-old son Carl (Josh Hutcherson) to know about—their destination is near a business meeting he is expected to give a presentation at—but as their trip within cramped quarters presses forward amidst one pitfall after the next, Bob rediscovers the importance of putting his family before work.

"RV" follows a course frequently traveled (in addition to "Vacation," there are hints of 1988's "The Great Outdoors" and 2004's rancid "Johnson Family Vacation") and is mostly a series of comedic set-pieces, but the cast is so winning and keyed into the tone director Barry Sonnenfeld is going for that they make it work. A duel with a gang of raccoons that have invaded their vehicle and a gross scene involving a storm of fecal waste are on the lower rungs of inspiration, but there are many other moments that work surprisingly well. When Bob makes the poor decision of taking the RV up a steep and dangerous mountain pass and gets stuck atop a sharp rock formation, genuine hilarity ensues as he tries everything possible to free the vehicle from its impossible perch. There is also an unfortunate run-in with a thunderstorm that leads to one of the family's first moments of bonding, a subtle bit involving getting around a slow truck without actually gaining ground on it, and some scenes that ring true where Bob has trouble getting the wireless reception needed in order to send out to his boss the proposals he has been secretly working on at night.

A running subplot involving an incessantly bubbly family of banjo-playing travelers, headed by Travis (Jeff Daniels) and Marie Jo Gornicke (Kristin Chenoweth), and the Munros' failed attempts to get away from them is very funny too, inventing some cute ways for these two night-and-day families to keep running into each other. Screenwriter Geoff Rodkey does a surprising thing with these characters that proves he has been working on a higher level than the television ads and trailers, overblown with dimwitted, frenetic gags, would suggest: he transforms them from caricatures into honest, kind and real people. Jeff Daniels (2005's "The Squid and the Whale") and Kristin Chenoweth (2005's "Bewitched") eat up their scenes with commitment, energy and crisp timing; they make potentially annoying characters not the least bit irritating simply from the joy they bring to their performances.

After impressively displaying his dramatic chops in a series of darker roles (2002's "Death to Smoochy," "Insomnia" and "One Hour Photo"), it is refreshing to see Robin Williams return to the lighter fare that made him famous. Because he hasn't been in this kind of amiable part in a few years, Williams' comedic shtick feels rejuvenated and is most welcome. A genius of improvisation and comedic delivery, Williams also injects enough heart into Bob Munro to make him more than just a walking one-liner.

Filling out the rest of the Munro clan are Cheryl Hines (2005's "Herbie: Fully Loaded") as wife Jamie, a likable foil for Williams in the same way that Beverly D'Angelo was to Chevy Chase in the "National Lampoon's Vacation" movies; Joanna 'JoJo' Levesque (2006's "Aquamarine") as moody but never outright mean daughter Cassie; and Josh Hutcherson (2005's "Little Manhattan"), easily one of the most talented child actors working today, as son Carl, who has turned to dressing ghetto, listening to rap music and lifting weights in an bid to compensate for his insecurities about his size and stature.

The Munros' trip to the Colorado Rockies can't compare to the Griswalds' journey to Wally World—by having to stick to a family-friendly PG rating, the film lacks the raunchy, un-PC irreverence of "National Lampoon's Vacation"—but "RV" nonetheless stands as a fond stepchild of the genre. The movie is over a little too quickly to obtain the heightened lunacy it desires, and the story trajectory is obvious from the get-go, but that doesn't mean the film isn't crowd-pleasing, undemanding fun. Its heart lies with the Munro family themselves; as written and performed, their easy, naturalistic, sarcastic, and at times innocently off-color give-and-take makes them feel like an actual family rather than a shallow screenplay creation. Also appreciative is the avoidance of schmaltz even when the proceedings have to briefly get serious in order to wrap things up with a moral about not taking your family for granted. "RV" is frothy, to be sure, and no one will ever accuse it of reinventing the wheel, but there has been a deficient place for a solid, silly, pleasing mainstream comedy that this film is happy to fill.