quite a long way to go with older people. Unless they have some special reason for wanting to go there (interest in colonial architecture, state socialism, Spanish language etc) perhaps you could do just as well closer to home? Cuban food is a bit of a trial and they've had two hurricanes in the last month. It's a fascinating place and I don't want to put you off but somewhere in Europe would be a lot easier for people in their 70s.
Not sure of the age tho (70's) -the flight was a trial having to go through Canadian Immigration as well- but Cuba was the most vibrant country I have had the pleasure of visiting.
Havana was a joy -we went on Revolution day -Fidel addressed a million people in and around Revolution Sq.
The bars outwith the hotel are vibrant -there is a divide between tourists and locals -but the young people -as the bars and music were outside- were salsaing to the music -it was like a time warp.
Loads criticise the food -we had a fabulous 5* hotel -fresh food 24/7 -staff who couldnt have been smarter nor more attentive -it was the experience of a lifetime for me -and the beach -a 2 min walk away in Varadero was simply the most stunning beach I have ever seen and was voted the best beach in the world -all for �800 each all inclusive -you cant whack it.
I wouldnt go back because quite simply I wouldnt want my memories of that holiday spoilt -it was very special.