ENBD Duo Query

I have the Duo Card.

There is the benefit of using it for getting 2 free Vallet Parking in a month given that 5k is spent.

But I want to know if the 5k should be spent on the Mastercard Platinum or the Diners Club Card? Or can it be in any one of the cards?

And in the Vallet which card do I present to them ? I am guessing it's the Diners card.