It would be tempting, though not exactly right, to call the Little Treehouse Play Cafe "Starbucks for Sprouts." Nor would it be completely accurate to call it "Chuck E. Cheese's, Hold the Cheese," though both get close to explaining the just-opened play space and cafe in Chestnut Hill.

Part coffee shop, part indoor playground, part Internet cafe, this is the as-yet partially realized vision of Rachael Williams - and the result of a good idea meeting a big opportunity, when indulging a passion means putting everything you have at stake.

For Williams, an ebullient Brit and classically trained cellist who left London for Seattle in the late '90s and moved to Philadelphia in 2002, that meant leveraging a handful of rental buildings that had provided her income and the house in which she's raising three adopted daughters. After more than $1 million for the purchase and renovation of an airy 6,500-square-foot, 1920s-era structure at 10 W. Gravers Lane, the business opened May 1 and now packs in crowds of preschoolers and their adult handlers. But it took a lot of worry and "mortgages on top of mortgages" to get there.

"I had been living off real estate, and when that market began to fail, there was a need to figure out what I was going to do," Williams said. Like many people facing the uncertainties of the current job environment and the strained economy, Williams said, "I either had to get a job, or do something I was passionate about."

She considered going back into media - having worked in publishing and TV production in the past - but the timing certainly wasn't right for that. Later she considered buying a Gymboree franchise, but decided she had a better plan: to create something she hadn't found in her travels with three daughters, ages 5, 4, and 2.

The idea was to have a place that was child-friendly yet not childish, where adults could meet and eat or have coffee (yes, there's Wi-Fi) while very young children play - no registration or sign-ups or commitment required.

You can't call it a day-care center or drop-off play place, as adults must remain with their children. And it's not like a Mommy & Me program because there's no structured activity. You show up, pay $7.50, and you can stay for a few minutes or a few hours.

Williams wanted to create a place that wouldn't simply tolerate young children, but would give them something to do - at the same time welcoming parents. Ultimately, the space will be more cafe-oriented, with full food service, brick-oven pizza, and outdoor seating. The basement will have a larger tumbling space, and the main play area will get larger play structures for climbing and sliding.

As it exists now, the cafe-area decor features warm colors and framed African tribal flags, with none of the flashing lights, noise, and electronic gimmickry of most venues geared toward parents and small children. The play area is devoid of giant soft-sided geometric shapes in primary colors, and a recent visit found not one toy bearing a button that, when pushed, cues up a tinny rendition of a Mozart sonata. The toys are made of wood and other natural materials and are the kind designed to encourage imaginative play: work bench, grocery store, little cars to push.

All of that, of course, depends on the business taking off, but it seems to be finding a niche: On the first rainy weekday after the grand opening, 120 customers (58 adults, along with kids) came in to play.

On feedback forms, parents are calling it a refreshing change of pace from kid-unfriendly coffeehouses and shops where children can look but not touch. "The Treehouse includes productive play, whereas going to a toy or bookstore is really centered around interacting with 'things' in the hope that the parent will buy something," wrote a woman named Pamela.

Yet the path from there to here was not all a happy circumstance. The first stage of the business began in March 2008 at a smaller location nearby on Germantown Avenue, in a space Williams leased. But a struggle ensued between the building's owner and the Chestnut Hill Civic Association over the landlord's plans to expand and renovate. When the space on Gravers Lane became available, Williams said she saw it as a giant risk, but the right risk at the right time.

That feeling - of wanting to create opportunity from uncertainty, and be passionate about one's work - is a common theme among the clients who call on Elizabeth Hechtman, a Philadelphia-area life and career coach. Williams is not one of Hechtman's clients, but Hechtman said her story shares themes with many people she counsels.

"Half my clients are wanting to transform the work they're doing into something else," something they're passionate about, Hechtman said. While many are among those facing a forced career change due to layoffs, others are earning good livings in secure jobs that they're just not wild about.

For a single mother of three little girls, the risk felt even greater. Hechtman said the key, for women especially, is to recognize and accept the support they do have, whether it comes from parents, friends, or a network of personal and professional connections. Create a plan, give yourself as much financial stability as you can - even if it means holding off for a while on your new endeavor - and then go for what you want, she said.

"Sometimes the best thing you can do is just go with your gut: When it comes right down to it, and everything's aligned, you have to ask yourself if you're willing to live with the decision," Hechtman said. "You have to be either young enough to live long enough to recoup it, or strong enough to live with whatever the worst-case scenario will be."

Going with her gut has been a running theme for Williams. Nothing about her choices, from adopting her little girls - two are African American, one was born in Vietnam - to where she ended up living and working, was carefully planned. When she wants something, she usually goes for it.

Take her response to a question about how she was able and willing to adopt three girls in four years - all as a single parent (although she's now engaged to a nice guy named Paul, whom she met on J-Date).

"Well, I knew I wanted three kids, and I knew I had to get on with it!"