My mom was 67 when we took the train from Cuzco to Macchu Pichu &her idea of physical fitness is to ring a bell &have a servant bring her tea! (Could be that's why I'm such an ardent backpacker/hiker/racewalker?) We didn't have time to do any high altitude walking here in the US before we left, but I recommend that you try this first. If you can get to anything over 8,000 feet &do some casual walking, you'll have an idea how you might react to 10,000 feet+.

Cuzco is at about 11,000 feet as I recall; Lima is at sea level. Most travelers stay a day or two in Cuzco, visit some of the nearby ruins &get acclimated. The train is a great way to get over the Andes from Cuzco &down into the Amazon basin where Macchu Pichu is located at about 7,000 feet.

Besides the altitude, the hardest part of walking around the ruins for an older person is the uneven terrain. I also suggest organizing the visit with an overnight stay at the Lodge at Macchu Pichu (room 40 is the best!) so the older travelers can go back to the Lodge during the day for a rest &therefore see the site in a more leisurely fashion.

High altitude reactions can include a screaming headache &slight nausea. In Cuzco, one can sip some herbal tea to relieve the headache. I've climbed mountains here in the US in our glorious Cascades &Mt Whitney in Calif, the Continental Divide in Colorado &only seem to get the headache &nausea over about 13,000 feet. (And now that Mt St Helens has blown her top, it's only an 8,500 foot climb &no sweat.)

If you've got a year, you might suggest a gentle walking program for your friends. It would make this trip easier, not to mention other health benefits.

Gail In Eugene but never for long...