Looking for recommendations for a new project I'm going to work on for a potential client

Hi

I'm going to work on a small project and I'm looking for ideas and recommendations:

Context:

There is a coffeeshop that gives out paper stamp cards to the customers (I go there pretty frequently as well). Every time the customer buys a coffee, they get a stamp on the paper and when they reach 10 stamps, they get a free coffee. However there is always an issue with this: most customers forget to bring the paper and many also lose it. So my idea is creating a basic system that allows the coffeeshop to email a unique QR code to every customer so that they can show that QR code to collect stamps.

I'm going to create a minimum viable product just to show them as a demo to see if they want to have it.

Tech:

I've done some research (I'm not a newbie but not an expert) and reached the following ideas:

Database

SUPABASE to store the users' and stamp cards' info (qr code, how many points, etc) - users sign up on the small tablet on the cashier's counter. There won't be any public login/dashboard system for the users. they will just use a link they receive in their email like website.com/api/points/{stampCardId} to see their points if they want to.

I've never used it before but I reviewed it now and it seems very intuitive and popular and performant.

Backend

Node + Express

Frontend

Next

Component library

ShadCDN

Does this sound reasonable? I don't want it to start with something complex when I don't know if they would even want it. Just something to show as a working demo. It's also a good learning opportunity for me.

Thanks