As a retirement trip, we booked (2years ahead) the Galápagos Islands (Inner Loop) and Machu Picchu trip with the Celebrity Xpedition as our ship in the Galápagos Islands. It was every bit of what we expected and more!
From our arrival in Quito, until our departure from Cusco to Miami, the Celebrity experience was awesome! Every step of the way, Celebrity had us involved with first class food, service, experiences, and entertainment.
As for altitude, the staff provided 5 minutes of oxygen to John when we stopped for lunch on our first day in Cusco. It worked, and his slight headache stopped.
The cabin was good for sleeping, as the daily activities keep you so busy outside of the cabin area.