Early in the slack, sentimental caper “The Wendell Baker Story,” Luke Wilson’s huckster hero leans out his car window to gaze goofily at his girlfriend, Doreen, played by Eva Mendes. Shaking her head over some latest bit of shiftlessness, she nevertheless beams at her lovable loser. You can supply the unspoken line: “Oh, Wendell!”

The moment serves fair warning that “The Wendell Baker Story,” which lolls along with the insouciant comedy of the featured brothers Wilson (Luke, who wrote and co-directed the film, and Owen), is a romance, but in a different mold: It’s a movie deeply in love with itself. But watching Wendell wend his way indefatigably to redemption (or at least serendipity), it’s hard to share the love, no matter how much the movie insists on his lazy good nature.

An affable, boundlessly optimistic Texas original, Wendell is a self-proclaimed “venture capitalist,” without much cooking in terms of ventures. When success comes, so does trouble, probably because his American Dream germinates with a fake-ID outfit catering to illegal Mexican immigrants and flagrantly operating out of a trailer by the border. “Who wants to get American?” Wendell asks, shortly before the inevitable police sting lands him in the penitentiary, still wearing his seersucker suit.

Oh, Wendell. Prison doesn’t stamp out his flair for glad-handing: The movie’s biggest laugh sees him brokering peace between gangs. Only the lost love of a good woman shakes Wendell out of his good ol’ boyhood. Doreen loses her patience and, as he learns, puppy-eyed, after his release, she has taken up with a new, responsible man (Will Ferrell, kept to the side in the Wilson show, in straight-man mode).

After solidifying Wendell’s cocky, rascally charm, the film turns to the new Wendell, meek but not beaten, shunted into work at a crummy home for the elderly. The proprietor of Shady Grove, Neil, is a kind of evil-twin opportunist to Wendell’s dreamer-schemer, and is played by Owen Wilson with appropriate evil-twin facial hair. While Neil skims Medicare checks, Wendell does his decent best for the neglected oldsters, who conveniently number various mascots of oldschool cool among their ranks: Harry Dean Stanton, Seymour Cassel, and Kris Kristofferson.

The key to enjoying our rascal’s progress would be the feeling of going along for a devil-may-care ride — you want the movie to communicate, as one critic said of Warren Beatty’s performances in the 1970s, “Watch this — it’s fun.” But, though nobody wants to start a family feud, Luke might not be the right Wilson for the job. Leaning on his signature Texas drawl and bemused deportment, Luke moves from slightly grating to ingratiating and spikes things with a punchy confidence that wears thin — and wears better on Owen. (Brother Andrew stays behind the camera, co-directing.)

You can see why Owen plumped up for the silly role of the elderly home villain. It’s prime fodder for his typically perverse style of underplaying. But leaving the lead to logy Luke means that things perk up all too noticeably when Messrs. Stanton and Cassel appear. Though their parts are overwritten with silver-foxy mojo (to the point of seducing 16-year-old store clerks), the two veterans telegraph more charismatic mischief with a dead stare and a twinkle in the eye than their young apprentices ever do.

“The Wendell Baker Story” settles into a wearisome final stretch that’s more “Secondhand Lions” than “Smokey and the Bandit.” In the great wide Texan open, golden with sunlight, Mr. Kristofferson’s fossilized fogey flies his own plane and helps save the day. Wendell, deserving or not, realizes his dreams of hotel management (sparked, in one of the movie’s undeniable fun touches, by a prison-library dime paperback of Conrad Hilton’s “Be My Guest”).

Like Wendell, “The Wendell Baker Story” is incapable of arousing true dislike so much as frustration and boredom with its ways. There’s still enough of the boyish Wilson charm that permeated Wes Anderson’s “Bottle Rocket,” which introduced the talented family to the big screen a decade ago. This time, however, their combined forces might be too much overachieving underachievement for one film to bear.