Asked to speak at Horizons for Homeless Children’s annual women’s breakfast, Nia Vardalos says accepting was a no-brainer. Though busy working on a couple of scripts, the actress-screenwriter said she couldn’t resist coming to Boston. (The event takes place Nov. 6 at the Westin Copley Place.) Her commitment to the cause of kids has less to do with her career in Hollywood — her best known film is 2002’s “My Big Fat Greek Wedding” — than with her bestselling book, “Instant Mom,” which she wrote after adopting her daughter. “I’ve formed this connection to strangers,” she says. “I thought I wrote an adoption story, but people come up to me and say, ‘That’s a book about my family.’ ” It isn’t, of course, but Vardalos says the memoir chronicling her adoption of a preschooler — with just 14 hours notice — found an audience because the themes are universal. (People also seem to respond to the behind-the-scenes Hollywood stuff, including a funny story about “Golden Girl” Rue McClanahan.) Vardalos says parenting has taught her a lot about the way the world works — or doesn’t. “Perhaps we should send Congress into a kindergarten class so they can learn to get along, share, and solve problem,” she says. “And then snack and a nap.” Meanwhile, next up for Vardalos is a screenplay for an anti-romantic comedy. “You know, like a romantic comedy making fun of a romantic comedy like [‘My Big Fat Greek Wedding’],” she says.