YYHWH,
Not to totally rain on your parade but at 8 ads per month you would have no ones attention. Typically in the world of advertising if you want the listener / viewers attention you will need them to hear your ad roughly 21 times in one week at a minimum. The next step is to ask when and where you would want those ads run? What quality of production do you want to have for those ads? There are so many more factors that will come into play that your proposal truly becomes an unrealistic prospect unless you find yourself a financial angel with deep pockets.
And this is all after you've decided what the message is you really want to deliver to the public.
Hiring a good PR firm with solid media contacts would be a better return on the money. Here you would have someone actively developing the image of your non-profit organiztion in such a way as to possibly get you interviews and additional free expoasure for the issue/s you wish to bring to the publics attention.
david
"Vision is the art of seeing things invisible"
Swift