When people are old and enfeebled and befuddled, perhaps demented, maybe with Alzheimer's disease, they need a lot of help, they are like babies, one could say.
Some churches help babies by having people outside the family also help--especially they are ready to help if one or both parents were to die.
These are godfathers, godmothers, or sponsors. The names vary.
I think it wise to use an institution such as that, one used for yougsters, for eldsters. Four post down on this page is a link to a video on YouTube that shows a ceremony, in wich godparents are appointed. https://www.youtube.com/watch?v=MTmNj56vF_A&feature=youtu.be
(Transcript of the ceremony about 6 posts down).http://godparentsforeldsters.blogspot.com/2011/09/new-how-godparents-for-eldsters.html