As a parent I am going through something similar myself. It is not hearing related however the "problem" has been going on now for six months with the AME not saying yes but not saying no to a medical.
As has been mentioned previously medical conditions and standards can change ( so can career aspirations! )
I would encourage his interest in aviation and when he is older and is going to apply for a flying job or that much more difficult job as an Air Traffic Control Officer :-)
I would make him take an independent, possibly private hearing test conducted by an accredited consultant.
You will then have a set of results which may indicate a class one medical is out of reach or you may have a set of results which the AME/CAA will look on in a favourable light.
This up to date report could save you money and more importantly time in the long run.
At the time of writing you need a class three medical to become an ATCO however I do not know if the hearing requirements are the same as a class one medical.
And while we are at it make him do the Duke of Edinburgh Award up to Gold. It will not improve his hearing but it will improve his interview chances!
