I'm going to Tanzania for three weeks in January, and have been told that sunglasses are an absolute must, but I wear glasses already. What's better, getting contacts and wearing sunglasses when I need them, getting those sunglasses that clip onto your glasses, or getting those glasses that turn dark in the sun? I'm worried those clip-ons will look dumb, but I don't know how practical contacts will be. I'll be sleeping in a tent, staying on a farm.