My automatic response to "Who Is In Charge Here?" is typically - "The Senior." (Unless you are standing in my home, in which case I would point to The Pug...) Whether they are making the decision in current time or through decisions discussed and memorialized in the past, the one in charge is the senior loved one.
This goes back to planning. Families must engage their senior loved ones in a conversation about their wishes and goals. We need to have tough conversations sometimes - mom and dad want to stay at home "til they come out feet first!" - and we cannot bend to agreeing or promising that this will happen when we just don't know how life is going to play out. If a plan is created and financial planning shows that it is an affordable option, well, then - it is just that, an option. If the financial plan does not support the expense of staying home, a conversation must be had regarding other options. Assisted living? Moving in with family? Dad finds a MUCH younger "nurse" to marry late in life?? (It happens! Have a plan.)
Beyond discussing goals and financial planning, a senior must establish who will execute this plan in the event they are no longer physically or cognitively able. This is accomplished through Estate Planning. I will defer to a competent Elder Law Attorney for specifics, but let me assure you one thing - the senior does not need to have an estate like the Biltmore in order to estate plan. Their ranch style home on a quarter acre estate needs a plan just as much! Part of estate planning is determining who will make decisions on their behalf regarding their finances and their health care.
The choice of Power of Attorney is very important to both the senior and any other family members. Choosing this individual should include a meaningful conversation with the elder law attorney who is drafting your estate planning documents. The Power of Attorney appointed serves as the decision maker in all areas they have been given power - such as selling a home, admission to a care facility, managing health care, and spending of money. The perspective of a neutral third party (your attorney) can be invaluable.
I've seen many people over the years who regretted not taking the time, or accepting the expense, to estate plan. Not paying an attorney cost them far more in the long run than they could have imagined. One's health, wealth, and legacy should not be left to documents purchased at office supply stores or downloaded from the internet.
So who's in charge? The senior and family who plans accordingly.