One of my general problems with tipping is that I have to tip before someone makes the drink. Then end up with burned coffee I tipped for. This feels the same.
If the customer ordered via the POS, it will be shown on the next visit, if they sign in with their phone number (which is used to save your order history for easy reordering).
I had a shop too once (print, Germany, sold it after a few years) and know people owning restaurants. As far as I'm concerned, you are supposed to get your feedback from the "meta data" of your business, not involve the individual customers my making them work. Which is very unlikely to give you true and/or good data anyway. It's like asking people for what they want as "market research", which just shows a lack of understanding of how brains work and way too much believe in the rational mind theory.
You seem to have created the anti-human coffee shop.
You don't need my number to sell me coffee. Asking for it is an invasion of my privacy. If you insist on an awards program of some kind, it already exists in it's ultimate form, the stamp card.
Customers should not be tasked with evaluating employees. They have no expertise in the matter.
Employees should not have wages effectively stolen from them under the auspices that "good work is rewarded". You know how you reward good work? Raises, profit sharing, more responsibility, benefits programs, you know typical things employers do for employees in a worker centered environment.
All this also assumes anyone uses these systems as intended. I doubt customers will select ratings in any meaningful way and you will have no way to ground truth if they do or not. Nobody will ever care enough to sit through customer interviews to evaluate whether your one question survey is valid or not. Certainly not for a cup of coffee.