Do a split of 4 days in Cuzco and 2 in Lima. You may go back to Lima, but chances are that Cuzco will be only once; therefore, to me, better to have extra time. I side with your friend in leaving Thursday morning--arrive on Wednesday and overnight at the Costa del Sol, then fly Thurs. early morning. As for stay, Marriott's El Convento was quite nice while Tambo del Inka really impressed me. In Lima, stay in Miraflores (get Uber from the airport). Stroll through Larcomar and el malecon, and of course, take a day for Centro de Lima. Enjoy the trip!