Giving your work to charity is fine, but only if no one else involved is getting paid. It's amazing how well-paid most charity organizers are, but also expect writers to work for free.
I have nothing against writing an article for a charity, but for the most part, why would a charity want anything else from a completely unknown writer? If you aren't known, and if you can't sell your work commercially, why on earth do you think it's going to generate any profit if you give it to a charity.
I got to thinking (eventually) of these same issues, James.
First: I'd want such an endeavor to be closely associated with and endorsed by an outfit like Charity Watch, for instance.
Second (part A): there seems to be lots of free/low cost short stories available on smashwords/amazon maybe/other sites that have buyers who purchase on the basis of user reviews, word of mouth/blog, etc.
Second (part B): The charities who would like to participate might want to get involved as endorsers and/or editors, especially if they produce their own magazines. For instance, they might want to publicize some writer's efforts (with permission, of course) that they support.
Here's one scenario I've been envisioning (which needs work): Someone says to other writers, Hey, lets all work on writing for The Nature Conservancy, for example. That group writes and critiques each other's work. They "submit" their work individually for consideration by The Nature Conservancy, which then selects perhaps all or some for their endorsement. Or they what? Vote by group (anonymously?) for the pieces they want to publish together to create, for instance, a book of short works, all donated for their chosen charity?
Charities whose concern is literacy might play a big role, yes?