Hi All (again)

I'm lucky enough to be off to Peru next year on holiday and am wondering what lenses to take/buy. I have a 450d with the 18-55mm kit lens and a 70-200mm f4 lens. I'm going to buy a canon 10-20mm or sigma 10-22 lens. I will prob leave my 70-200mm at home as my travelling buddy is taking the 100-400mm. I'm thinking of also buying 50mm f1.8 and leaving the kit lens. Does anyone have any thoughts?

Thanks all in advance,

Edd