Poor does not necessarily mean unequipped, and this is something you can teach. I don't really have a full image of what "poor rural US" looks like, but I come from a European village and I can tell you everyone in my village did some sort of farming/gardening and/or animal husbandry, be it pigeons, chickens, sheep, etc. One thing that the solarpunk community does extremely well is adapt the agricultural topics for a more "modern" audience, i.e. people living more in flats or without access to good soil.
An educational activity that would take a while would be a grower class for kids, maybe sponsor the initial investment for something really accessible: 1 pot, some soil, nutrients, stuff like that. If the library buys in bulk, it's going to be cheaper, plus I'm thinking a family cannot easily justify buying a 20lbs bag of soil if they have no place for as many pots. If these initial things are provided (and maybe kept in the library), people can be more relaxed about the outcome.
You library people are good at research. I believe that if you just provided a course for kids and families saying "this is what you can plant easily and here's some materials to get you started," that could do part of the trick. As [@tinker](https://infosec.exchange/@tinker) often mentions, a seed library is a great way to get people interested, because after the initial seeds are bought, they will be multiplied by people handing them out.
Any topics not usually taught by the school could also be a way forward. IT, maths, any topic you think could be beneficial. In that aspect, since it can be taught over longer distances, I think you have all of Fedi to help with that. I raise my hand!
Providing materials and infrastructure for discovering new stuff is the way, I think, in any case. Even if it's "just" soil and seeds. I don't know what's lacking in your area, but whatever it is, may be supplemented by the local library.