My solution: let my parents stay in US

I have the same situation: no siblings. My parents are over 70 years old, they are in US now with greed cards. So far they are healthy and happy. They go to school to learn English everyday and play at a senior activity center with friends a couple of days a week. They stay in a senior housing in downtown area with subsidized rent, they can easily go to anywhere by bus. There are more than ten Chinese senior couples living in the same building, so they can easily organize many activities together. We are lucky the state they are living has medical coverage (even the medical insurance premium is covered) for senior (> 65 years old) green card holders. They periodically go back China to visit relatives and friends.
I don't know what'll happen if they'll be disabled and can't take care of themself. I'd like to know more from you guys. Any information and suggestions will be highly appreciated.