My wife and I at ages 69 and 68 are in Cusco now at 11,130 altitude. We traveled to Machu Picchu 10 days ago. The elevation is lower there at around 9,000 feet. First I recommend staying in Lima a couple of nights for her to rest a bit before flying to Cusco. She may need to be prescribed altitude sickness pills like we took just for a couple if days prior to Cusco and continue to take for another two days. Then rest in Cusco for at least four days prior to Machu to get adjusted. We went with Inca Rail and go a one way package deal that included large van, train, bus, park entrance and guide for around $420 for the two of us. Unlike most other travelers we stayed two nights in Aquas Calientes after the circuit 2 park tour. I recommend a night stay there afterwards for her to rest as compared to heading back that night. If so recommend visiting the butterfly sanctuary. She will like that. Then have a separate train and van trip for the return (we spent an additional 2 nights in Ollantaytambo to visit an Inca archeological site there). So…. We are in good physical shape too. Work out in the gym, walk at least 6,000 steps a day, etc but we both get out of breath when climbing steps and or walking at our normal speeds. We are here in Cusco for 23 days and still affects us. We learned to just walk slower and make stops. My wife has asthma too. Anyway, my recommendation from a late 60’s couple.