Stayed at their sister
hotel the Grand Aquarium the past 2 years and they use the wrist bands too.
To be honest I was a bit wary about the wrist bands at first but after using it I thought it was a great Idea. Stops you having to carry cash with you.
You put on the amount that you want at reception and every time you buy a drink or a meal you get a receipt with what you have spent and what your balance is. Very easy to track so you dont get overcharged.
You just top it up at reception as/when you need to. As someone else stated change your money else where as you will get a better rate.
I hope this helps put your mind at rest about wrist bands, I,m sure you will enjoy Club Aquarium.