Thanks for the replies everyone. She is in her 70s as well and has had a problem trying to find one for her age group, although she is active, the activity level can't be too intense (ie walking for many hours every day, etc). I think she can build up capacity but she hasn't traveled in many years, so I want to find the right group with an easy first trip and then go from there.
Any suggestions besides OAT? Any travel destination recommendations along these lines?
Thanks again all. Very much appreciated!!