Is there a legal document in which an 80-year-old woman in full possession of all her faculties can designate one, and only one, of her five children to act on her behalf should she become incapacitated? We want to forestall a "committee of five" bickering and arguing on what would be best for our mother if she is not able, physically or mentally, to take care of herself.
Encourage your Mom to make two documents. As long as she is of sound mind, she can make a durable power of attorney for finances and a durable power of attorney for health care. In these documents, she can name whomever she chooses to represent her if she becomes incapacitated and unable to make her own financial and medical decisions.