OP, your informal reps don't refer to feeding your baby, instead they give the following timeline:
You started charging at 9.59;
Your class started at 10am;
The class was scheduled to last from 10am to 11.30am;
But the class was cancelled;(from your first post, not the reps)
The PCN was issued at 11.29, 90 minutes after you parked;
During this period we don't know what you were doing, but do know that you could not have been feeding your child for this period.
IMO, as regards the contravention you do not have a defence and the Equality Act has no bearing on this case at 11.29am.
I think we would need to look elsewhere for a defence.