Cutesy little gimmicks and devices are plentiful in “Beginners.” A Jack Russell terrier speaks in subtitled English, for example. A man and a woman on a giddy date skate out of a roller rink and back to the carpeted hallways of a downtown Los Angeles hotel. And fast-paced, narrated photo montages help illustrate a childhood, and a marriage, and a life.

On paper, it all could have been too cloying or self-conscious, but writer-director Mike Mills finds just the right tone every time. He also draws lovely, natural performances from Christopher Plummer and Ewan McGregor as a father and son who are finally getting to know each other, truly, toward the end of the father’s life. And Melanie Laurent shows a softer side here, and an effortless gift for comedy, as the young woman who teaches McGregor’s character how to fall in love, for once, as a grown-up.

McGregor stars as Oliver, a graphic artist who’s remembering his father in flashbacks at the film’s start. Plummer, as Hal, has just died of cancer. And yes, this is a comedy — because at the same time that he announces he’s suffering from the terminal disease, he also declares that he’s gay, and that with the passing of his wife of 45 years, he finally feels ready to come out of the closet and reveal his true nature.

Plummer embodies that sense of wonderment, an openness to whatever new adventures may be in store, from a much younger boyfriend (a sweet Goran Visnjic) to movie nights with his new pals to the thumping beats of house music. He breaks your heart with his willingness to make himself so vulnerable later in life, and Plummer never lets the character devolve into some promiscuous, flamboyant stereotype.

A few months after Hal’s death, Oliver meets Laurent’s Anna, a French actress who’s in and out of town for work. They’re at a costume party where he’s dressed as Sigmund Freud and she’s dressed as a vagabond — only she has laryngitis, so she has to answer all his questions by scribbling notes on a tiny pad. He’s sad, sensitive and withdrawn; she’s cute, clever and flirty.

Mills moves seamlessly between past and present, as Oliver allows memories of his father’s newfound happiness and love to influence his own relationship. He beautifully conveys the way the past comes back in snippets, in etched images and pieces of conversation. This is especially true of Oliver’s recollections of his mother, a cool, playful woman with an offbeat sense of humor played memorably, in just a few scenes, by Mary Page Keller.

Her performance is yet another example of how “Beginners” could have been too wacky, or populated by caricatures. Instead, it’s surprisingly observant, dryly funny and tinged with melancholy — just like the movie itself.