Meh! You appeal as the keeper. No blabbing the drivers identity. They do not know who the driver is. They only know that you are the registered keeper. They have not issued an NtK that complies with PoFA and so cannot transfer the liability for the charge from the unknown driver to the known keeper.
Use this wording for the appeal (also known as the "go sit on sharp stick and rotate" protocol) and make sure you don't tick any boxes that says you, the known keeper were the unknown driver.
I appeal as keeper. I am not obliged to identify the driver and I decline to do so. You are unable to transfer the driver’s liability (if any) to me because you have not relied on the provisions of Schedule 4 to the Protection of Freedoms Act 2012 (PoFA) to be able to hold the keeper liable for the charge. Furthermore, it is now too late for you to deliver a PoFA-compliant notice to keeper.
The registered keeper cannot be presumed or inferred to have been the driver, nor pursued under some twisted interpretation of the law of agency. Your NtK can only hold the driver liable. PCS have no hope at POPLA, so you are urged to save us both a complete waste of time and cancel the PCN.
Easy peasy.