Hi Alex,
I'm not sure this should be framed as a call to action ("Contribute to ..."), first because the linked grants page does not actually explain how one can participate, and second because it appears that the contest has not started yet.
Also, what's the source for the primacy claim (Africa's first continental photography competition)? Can we be certain that, say, National Geographic didn't hold a photography competition for all of Africa in the 1970s?
I would suggest something lioke this (promoting their new Twitter handle too)
Twitter:
FB/G+: (not sure whether they have a FB page we could link to)
The first ever "Wiki Loves Africa" photo competition is in preparation, supported by a projects and events grant from the Wikimedia Foundation. Submission will be welcome from the entire continent.
This year's theme: "Cuisine"