If you are single, only your Conservator would have that authority.
Again, if you haven’t planned, nobody can act for you until the court appoints a Guardian and/or Conservator for you. If bills, such as your son’s tuition, need to be paid in the interim, a friend or family member would have to use their savings or borrow to pay the bill.
A court would have to appoint a Conservator. Nobody but the Conservator would be able to act for you.