For Boston-area Irish musician Shannon Heaton, invention was the necessity of motherhood. In the first weeks after her son Nigel was born two years ago, Heaton – like many a new parent – often found herself up at all hours for feeding, changing, and comforting. To help herself stay awake, Heaton made fanciful sketches of frogs and toads, and invented little stories about them for her own amusement.

Heaton didn’t envision that these wee-hours-of-the-morning creative exercises would someday become a full-fledged musical project. But this month, she will debut “Trad Kids,” a “folk musical” that combines storytelling, theater, singing, music, and audience participation. The 40-minute production, aimed at children in the pre-school to early elementary school range, will take place on Sept. 15 and 22 at 10:30 a.m. at Club Passim in Harvard Square. Joining Heaton – who sings and plays flute and accordion – will be her husband Matt on bouzouki, fiddler Cara Frankowicz and guitarist Andy Cambria, plus Matt Smith as the narrator.

The story of “Trad Kids” is disarmingly straightforward, explains Heaton: Bookish, wistful Agnes P. Mouse decides to overcome her solitude and have a “Cupcake Ball” with three neighborhood acquaintances: a sociable frog with a bright, infectious outlook, a shy, polite toad who loves to paint fish portraits, and a whacky lizard who loves trucks and magic tricks. The four hit it off so well they decide to form a band.

“There are some lessons in the story: conquering your fears, reaching out to others, and working together as a team toward a common goal,” says Heaton. “But it’s also about getting kids to understand that music is for everyone -- it’s not just something you sit and listen to passively, it’s something you get up and participate in, and enjoy.”

Accordingly, “Trad Kids” has plenty of opportunities for children (and their parents) to join in the fun, including singalongs and call-and-response games. Much of the music and other facets of the show draw on, or are from, Irish tradition.

“We’ve created larger-than-life characters who get kids’ attention, and lots of fun stuff they can zero in on,” says Heaton. “The littler kids think it’s silly; the older kids like it for the jokes and tricks, especially from Lenny Lizard. We want this to be something the whole family, including parents, can appreciate.”

Heaton’s idea for “Trad Kids” began to coalesce as Nigel grew older, and as she and her husband sought to find children’s music that would be entertaining but also appeal to kids’ imagination and intelligence -- “Fun doesn’t need to mean dumb,” she says. As she thought more about the elements that make for good children’s music, Heaton found herself recalling the toads and frogs she had sketched during Nigel’s first weeks. She brainstormed with her friend Ryan Hembrey, who had experience in musical theater, on creating a neighborhood of characters and a story for them, as well as songs they could sing.

(Inspiration for some of “Trad Kids” also came from other sources, Heaton notes: Lenny Lizard shares Nigel’s ardor for trucks, for example.)

Finally, this past spring, Heaton began to assemble the various musical, recreational and theatrical components into a show, and recruited friends to help stage it. While there are no immediate plans for any “Trad Kids” performances beyond this month’s dates at Passim, Heaton wouldn’t be adverse to the prospect.

Heaton says the experience of creating a children’s music production also has helped her in her “other” career. “When you play music for kids, you have to put the story and the emotions right out front, so they can respond,” she explains. “So now, I think more about the songs I sing when Matt and I are performing for adults: How can I bring out the joy, the sadness, whatever feelings are in a particular song, so the audience will be engaged and their imaginations will be fired? It’s fascinating how working from the perspective of children can also help you on an adult level.”

Admission to “Trad Kids” is $10 for parents, $5 for children. Says Heaton, “Babies are free, of course. It’s okay if babies fuss during the show. It’s okay to nurse during the show. It’s important to take tiny kids to hear music and see art, even if they make noise.”

For reservations or other details, see passim.org.