I understand your frustration but believe it or not, AEFs can not control the weather and, as we all know, this can change in a matter of hours.
I’m sure you’d be royally miffed if you were cancelled on a Thursday due to the forecast to wake up on the Saturday to find the sun shining and glorious blue skies.
We have a tendency not to call off flying until cadets get to us unless it’s going to be a dead certainty the weather will be bad.
Unfortunately the AvMed form is a requirement. I have the email address of the chap that wrote it if you’d like to send him your thoughts. The 3 month life span allows for any changes in the cadets medical history over that period. The form is pretty straight forward if parents take the time to read it rather than just ticking what they think is correct.