As Australia has one of the highest wage rates in the world, the highest fir casual workers, I think it is poor form to expect to be paying a surcharge as well. Asking to pay a surcharge for public holidays is quite acceptable. It should also be made quite clear to patrons before they order...
I am a depression & anxiety sufferer. I have been in situations where I have thought about taking my own life if it weren't for my friends support & encouragement, things could have gone bad. Yes, I'm OK atm. 🙂