What are you using the donations for if people are bringing old computers for free to your door step? Do you pay a lot of money for shipping costs to African countries or the goods will be transported free of charge as you are a charity organization? What do you think about Raspberry Pi Zero the $5 computer? You could get a whole bunch of them for less than the shipping fees on these old PC's you are sending out right?
I'm not at liberty to say how the bitcoin donations will be spent as it will be a joint decision.
We did an assessment last year and found that we could deliver computers at £10 per unit to certain places where it may have cost £80 to buy similar spec machines locally. So it makes financial sense and also saves computers in the UK from being scrapped.
We are big fans of the Raspberry Pi at the Turing Trust. Later this year we'll have finished our first off-grid classroom made from an old shipping container fitted out with Pi's and a PV solar system. You can read more here if you are interested:
http://turingtrust.co.uk/the-turing-trust-e-library-2/the-solarberry/Thanks