My own son will have to take French and I will support him 100% in doing that, but he has no natural aptitude for it and spends probably about 70-80% of all his homework/study time desperately revising this subject alone, to little avail. If this was a core subject of importance, I would accept that - but he certainly has no plans or wish to use French again once that all-important certificate comes through! It just seems a strange use of 5 years of time and effort.
When I was young and schooled in France, my first MFL ( at 11) was German to which I added English at aged 13 (with Latin and Greek though I was an exception to have a fourth 'foreign' language in my school as it is not in the curriculum - the children have to choose between Latin or Greek). My parents had pleaded for that and the headmaster was an intelligent open-minded man who arranged the timetable just for me to do these extra-studies... (His son two years younger than me did the same! I am pretty sure he had that also in view!
What a shock I had when I arrived in the UK and realised that classics are only taught in private schools! You could be surprised at my reaction as Latin and Greek are not really useful nowadays (except for knowing some Greek roots in medicine, etc., but frankly we can do without learring Greek for several years).
I saw the book a young girl uses at KEHS and I really loved it
and this pupil does
enjoy Latin .... Personally I really have excellent and fond memories of all my times studying Latin, Greek or German even though like you, I have completely forgotten these languages... I am not sure everything we study at a young age must
be linked to something in the adult sphere. There is the pleasure to learn, to discover different cultures, etc...
I feel it is really important to have an enthusiastic attitude so that your child could pick it up (instead of him repeating after you' What's the use of learning French?'
I have a friend who hates German (though she never studied it) and she often makes fun of it when talking about choices in MFL. Sure enough, her son didn't pick up German when he had this possibilility while starting year 7 (he chose Spanish instead)
The parents' attitude can create the child's attitude...