Hi Max! I had some experience volunteering a few hours a week at some great non-hackerspace nonprofits over the years - an adult literacy center (Philadelphia Center for Literacy), another place that tutored homeless kids (LA School on Wheels), and after that a place that focused mostly on writing for kids (826 Valencia in SF). At Noisebridge, I gave classes on Machine Learning periodically for almost 2 years.
From those experiences, I found that being application driven (opposed to theorem driven), and having personalized one-on-one or many-on-one instruction was pretty effective. I expect the students to have diverse needs, from studying for the GED, to learning enough math for parents to keep up with their child's homework, to people who want to learn math just for fun. I'm also hoping to move people to the computer a bit more as well, using python to construct and visualize basic functions (think like f(x)=x^2), and to learn very basic programming techniques, like variables, arrays, and for loops.
There are many massive online courses these days, and sometimes at Noisebridge ML people have formed small groups to work through those courses, which is one way to "scale" to the level of a hackerspace. I don't have a more specific strategy right now, and am also comprised primarily of ears and interested in hearing other people's ideas.
mike