Quite a difficult one there.
A cheap computer that's purpose is to be distributed to every child in every school.
How utterly awesome would that be with Ubuntu/Lubuntu on there?
Ubuntu was the Linux OS that, to me, finally proved that Linux was ready for the non-geek.
And to tie yourself to the schools, that would be brilliant.
But at the cost of diluting your focus.
Personally, I think it would be a good idea to at least give a little resource to getting Lubuntu (+Unity!! 8D) up and running, or maybe LXDE Edubuntu remix?