Definitely I would go with doing a Star Alliance award, flying through IAD -> ACC, or doing a flight on Lufthansa through Frankfurt. Using BA miles will get you hit up with a fuel surcharge.

I live in Accra, so please let me know if he needs any help.

Using ATM's will work to help fund your kid. If he is at Legon, sign him up with a Bank of America account. Bank of America has an agreement with Barclays to have free, no international fee access to their ATM's here in Ghana. There aren't too many Barclays compared to Ecobank, but there is one in the main campus at Legon.

I would probably discourage the use of any credit cards and ATM's that aren't from the main banks, and from using them at any store, as Ghana is a high fraud environment.

If your kid wants ethnic foods, I can show him where the nice spots are.