80 years old person, is suitable go to jiuzhaigou/huanglong

If your parents are healthy enough and do not have diseases, it is suitable, but it is still suggested to prepare some medicine for the altitude sickness in advance.
You can join a local tour, of course.
It is not suggested to go to Huanglong.

Hola Monica, can you be more specific about local tour, is it provided by a local travel agent there in JZG? Can we just book a local tour upon arrival at the jiuHuang airport or should inadvance. Is it like one day local tour or halfday? Can you tell me how much it cost. I plan travelling to Jiuzhaigou on this Mid of Oct 2013. Gracias

For local tour, I mean the tour from Chengdu instead of JZG.
In my opinion, if you want to travel well without any worry, booking a tour in advance is suggested.
To that valley, usually it is an one day tour, otherwise, it is hard for you to enjoy the beauty of the valley.
The price varies according to different tour agency. Last time, I joined a tour from TravelChinaGuide, which including the Chengdu, Jiuzhaigou, Huanglong and Dujiangyan and the expensive is around 1289US$. I think you can consult many tour agency to find reasonable price for you.