The Wimpy Kid meets “National Lampoon’s Vacation” in “The Long Haul,” the fourth film in the series based on Jeff Kinney’s children’s books that began in 2010 and now resumes after a half-decade gap. Getting away from hometown and school, the plot—based on Kinney’s ninth volume—hinges instead on a long family car trip, which of course turns into a series of slapstick disasters prior to the obligatory happy ending. The Griswolds would certainly understand and sympathize.

The cast, it should be noted, has necessarily changed after five years. The titular wimpy kid, Greg Heffley, was played in the first three movies by Zachary Gordon, who’s now literally of college age, so he’s been replaced by Jason Drucker, and his older brother Rodrick, originally played by Devon Bostick, is here Charlie Wright, while twins Wyatt and Dylan Walters alternate as their toddler brother Manny. Their parents have changed as well: instead of Steve Zahn and Rachel Harris as Frank and Susan, we have Tom Everett Scott and Alicia Silverstone. But director David Bowers, who helmed the two previous installments, returns for the ride (as does composer Edward Shearmur, as well as cinematographer Anthony B. Richmond and editor Troy Takaki), and the black-and-white animation inserts modeled after the illustrations in Kinney’s books reappear too.

In reality, none of the changes—or holdovers—matter much. The newcomers in the cast are more than up to the admittedly modest requirements of the franchise—as Greg, Drucker is an agreeable kid, and Wright (despite an internet campaign criticizing him) a thoroughly adequate Rodrik (made dumber this time around), while Scott and Silverstone bring typical clueless-parent vibes to Frank and Susan. (Fair warning: though Owen Asztalos is prominently billed as Greg’s sidekick Rowley, the character is pretty much sidelined this time around.)

And given that the screenplay was written by Kinney and Bowers, it’s predictable that “Haul” remains very much in the tradition of the earlier “Wimpy Kid” movies—a formulaic blend of slapstick and sentiment that youngsters up to age ten or so will probably enjoy, though it’s not much superior to the sort of teleflicks they can regularly see on kids’ cable channels. Parents might find the icky quotient rather too heavy—there is lots of potty humor (beginning with Greg’s unfortunate YouTube fame as “Diaper Kid”), as well as some upchuck moments (and fart-based scenes) to endure; a sequence is a run-down motel also goes pretty far in its depiction of seediness. On the other hand, there is at least one near-inspired moment directed specifically to them—a kid-friendly imitation of the shower scene from “Psycho,” down to Bernard Herrmann’s shrieking violins.

As to plot per se, there isn’t much. The family road trip is not only designed to take the clan to grandma’s ninetieth birthday, but to provide a chance for them to give up their electronic devices and bond for real over shared fun like a visit to a county fair (where a cute little pig enters the script, though it invites more scatological jokes). Her plans are thwarted at every turn by her unruly brood, however, and especially Greg, who wants to divert the drive to a Comicon-style convention where, by getting a one-on-one with podcast gamer sensation Mac Digby (Joshua Hoover) he can remake his net image following the “Diaper Kid” debacle. The other major thread involves a running series of confrontations with another traveler, a slob the kids call Beardo (Chris Coppola), whom Greg has managed to offend (along with his unruly family) at that cruddy motel. Both offer ample opportunities for the goofy, mildly gross-out episodes that are the movie’s raison d’etre.

“The Long Haul” is by no means a great family movie, but like “Vacation” (the 1983 original, of course, not the wretched recent remake), it will hardly be as painful an experience for the parents and kids who watch it as their journeys were for the Griswolds and Heffleys. It’s not appreciably better than the first three installments in the series, but no worse either; so if your children like those earlier movies, they’ll probably enjoy this one too.