A power of attorney requires the express permission of the person granting that power; and since your mother is already incapacitated to grant that, the best recourse for your father to be able to better manage the properties is to apply to the court for conservatorship. Being a conservator is the closest one could get to being given the power of attorney in terms of managing another person’s asset or estate.

Consult with a family lawyer for more information on the process of application for conservatorship, what steps to take, or if there are other possible options available for your case.