While neither a full-throated R-rated romp a la “There’s Something About Mary” nor a fully realized romantic comedy, “Wedding Crashers” contains enough appealing elements of both to catch the bouquet in what’s been a relatively humor-deprived summer. Pic starts slowly, peaks in the middle and can’t quite sustain that energy through to the satisfying finish, but there are enough laugh-out-loud moments for New Line to toast to healthy traffic down the aisles.

A too-long montage (one of a few) introduces John (Owen Wilson) and Jeremy (Vince Vaughn), two divorce arbitrators who have mastered the art of crashing weddings, an event that causes female attendees to “throw their inhibitions to the wind.” Their well-practiced routine is full of carefully plotted approaches — from dancing with the flower girl to expressing their fondness for Oprah’s book club — for capturing women’s vulnerable hearts just long enough to entice them into bed.

That’s all a prelude, however, to the main event: The wedding of the daughter to a well-connected Washington politico, Secretary Cleary (Christopher Walken, at about two-thirds speed), where John gets struck by the proverbial thunderbolt upon seeing the good secretary’s other daughter, Claire (“The Notebook’s” Rachel McAdams).

Jeremy, meanwhile, seduces a third daughter, Cleary (Isla Fisher), though the love-’em-and-skedaddle act gets thrown for a loop when John accepts a weekend invitation to the Kennedy-esque clan’s vacation home, hoping to extend his chances of wooing Claire away from her pugnacious boyfriend (Bradley Cooper).

What proceeds is fairly amusing, fitfully over the top and — in a series of gags about the Cleary girls’ creepy brother (Keir O’Donnell) — occasionally a touch homophobic. Most of the gags are drawn from the playbook of rich folks’ eccentricities, from the foul-mouthed grandmother to the horny matriarch (Jane Seymour) who takes a “The Graduate”-like pass at seducing John.

Jeremy, meanwhile, endures an increasingly bizarre array of indignities, from a full-contact game of touch football to a memorable under-the-table dinner sequence that takes “Goodbye, Columbus” up a couple of notches.

Director David Dobkin and writers Steve Faber and Bob Fisher have the wedding trappings and psychology of the ceremonial seduction down pat, but they’re on less assured footing in selling the John-Claire romance. Fortunately, McAdams is such a beguiling presence she helps fill in narrative gaps and actually creates a real character — a rarity for females in one of these lad-mag escapades.

While Wilson spends much of his time pining, Vaughn’s rapid-fire dialogue yields most of the comedic highlights, from labeling a woman a “Stage 5 clinger” to his hushed reverence toward the fellow who originated the wedding crasher’s art, leading to the inevitable (and after the first glimpse, pretty ho-hum) celebrity cameo.

Walken has too little to do as the powerful-but-doting dad, while Cooper’s boyfriend is such a sneering cartoon it’s a little too easy to root for Claire to dump him. And while it’s mentioned more than once that Wilson and Vaughn aren’t that young, they probably are a tad old for this brand of shenanigans, especially since they conveniently encounter so few husbands and boyfriends as obstacles.

Yet even with those minor gripes — and the larger one that the movie, like many a wedding, drags on a bit too long — it’s mostly an agreeable ride, with a deftly assembled soundtrack and even a rather sappy message about true love underlying it all.

Indeed, “Wedding Crashers'” real secret is that despite flashes of nudity, crudity and mockery of women’s raging hormones at the first sight of a trousseau, at its core it’s just a big pushover with the heart of a chick flick.