Hello Karthik, lovely post. I recommend you to check out what the guys at MEER are doing. This non-profit org focusses on installing solar reflectors in low-income countries. Note that their solution serves both adaptation and mitigation purposes, as it contributes to lowering temperatures while marginally increasing the albedo effect. The approach promises to be cheap and scalable; what's more, the technology is passive, i.e. does not need electricity access. 
I would really love to see more work done on what would climate adaptation projects need to accomplish in order to make GiveWell's list.