Bitcoin cafe with loyalty card

So,
I'm starting a coffee importing and roasting business. So far we are importing beans from Colombia and Indonesia.
I've been trying to get people who run coffee shops interested in accepting bitcoin. My question is about the feasibility of a loyalty card. It works like this: You get a card issued to you at the cafe nearest your home or work. You send say, one bitcoin to the address linked with the card. This recharges your card, so you have credit for 30 coffees. Each time you come to the cafe, you just run your card on the scanner, and it deducts the credit from your card. This way you could avoid having to wait for the confirmation every time you buy a coffee.

Would a payment system like this be expensive for small cafe owners to implement?

What might some issues be with it, security, computing, etc.?

Is this a good idea? Anybody want to be self employed, love coffee and socializing? Open a bitcoin cafe and buy premium coffee from us with bitcoin for a discounted price! We will beat the prices of the competition for comparable quality, guaranteed, in the interest of spreading the use of bitcoin for everyday purchases.