Actually, the AOPA course involves 8 hours of dual with a qualified flight instructor, so there is no reason why that time should not be logged in case Rev's father becomes keen and decides to pursue his own license (you never know, it happened to Alex Henshaw's dad!). I believe that in the eyes of the CAA, his father would not be a passenger but a student.
Anyway, it looks like the primary objective is:
(1) to make his father feel more comfortable about flying as a passenger; and
(2) to provide his father with some basic knowledge and a few skills, so that he can provide assistance with the navigation and radio work.
Such ambitions are quite reasonable and realisable. The American AOP has for many years offered a
Pinch Hitter course that is well thought of. The UK AOPA syllabus looks broadly similar, and I would think that it would be a great idea for a regular flying companion.