Ok, my first ever post, so here goes...my boyfriend and I just got back from Peru. We actually, in a roundabout way, ended up with a private driver. Long story, but I can explain how we found him if you are interested. Just PM me for the whole story.
He took us to Olly from Cusco and stopped at any and all places in between that we wanted to stop on the route (Salineras, Moray, etc) and even offered additional suggestions on places to stop that we didn't even know about. Spent about 5-6 hours with him and cost us $70. He also picked us up from Olly when our train got back and we took the opposite route back (Pisac, all the ruins near Cusco, etc). It was about a 6-7 hour trip back and we only paid $70 again. I felt completely safe with my belongings with him. Only downside is that he spoke only a little bit of English, so you may want to know some Spanish. I just used what little Spanish I remembered from back in my school days and it was sufficiant enough. If you are interested in his contact info or the hostel that got us in touch with him, I'm more than happy to give it to you. Just PM me.