Way before I ever tried, I had seen videos of RFID "contact less" demos where you tap the device to the machine. Like at a gas pump. The icon usually gives you a clue to tap as well, but I suppose you have to imagine it is even a theoretical possibility.

I don't think there is way to make it discoverable without a big sign saying tap here ↓. Not from the phone anyway. Just something children will see and in the future never think twice about.