So you want a Mickey bar. Cost is say $3. Present a credit card and you're hit with a transaction fee of 3% or a minimum of $5. If that's OK to you, then great. I don't think many people would pay $8 for an ice cream.
So a family comes to the parks for a day, brings $200 in cash. Then they find they cannot buy anything to eat. That's going to go down well. It is not that uncommon.
Amongst overseas visitors, the vast majority (95% and more) stay offsite. Their only choice would be to use a card. I use a currency card, which I load from my bank account. The transaction fees are therefore based on how much I load, not each time I use the card. But not everyone has them.
There is no way they could go completely cashless in the parks. And I have seen
@peter11435 's post suggesting they might.
Here's the First likely scenario. Family turn up to Boma, have their meal, and present CM with cash. I bet you anything the CM will find a way to accept this if they have no card on them!
More likely this could happen at The Mara. Having gone to AKL to look around, they decide to head to the Mara, where order their pizzas, pick up drinks and zebra domes, go to the till and get out cash to pay. Now what?
I wouldn't like to be a CM at AKL when this first comes into effect.