I'm taking a trip to Peru as well, my tour company accepts paypal in addition to Western Union. They add 6% to the Paypal, but to me it was a small price to pay for some comfort. Ask if they will accept paypal?

To me there are just so many bad, terrible stories about Western Union being used by scammers, I was turned off from using them. Also they're not without fees to be used, and of course you might be hit with cash advance from your CC.

Check if they have paypal as an option, and then use your CC on top of Paypal, for ultimate protection.