Your retained counsel can handle this. That is why you have a retained counsel. Polite to let the appointed counsel know so time is not wasted on your case.
We do not have a client/attorney relationship until you make an appointment, we discuss your case face to face, I accept a retainer, and we explictly agree to enter into representation.
You have no obligation to take the court appointed lawyer. Have your privately retained lawyer enter his appearance on your behalf, and the court should take the court appointed lawyer off the case.
This should not be a problem. Just inform your privately retained attorney and have your father contact the court appointed lawyer and let him know that the family is paying for a privately retained lawyer. If this case is in Fairfax Circuit Court, your father probably was assigned a full-time public defender to represent him. They will be cooperative. This is not an uncommon occurrence.
Have your retained attorney submit an Order of Substitution to the appointed attorney. Call him and tell the attorney you have been retained and entering an appearance. Most have no problem signing an Order of Substitution.