Three visits. That is the point where someone has decided they like the place and has not yet started taking it for granted. Ask for a Google review on visit one and you get nothing or a polite four stars. Ask at visit three and the words are better.
The booking system knows the count. On the evening of the third check-in, a short message goes out with a direct link to the Google review page and nothing else to click. One message. If they do not leave a review, there is no reminder, because the second ask is what makes people stop reading.
Referrals are the other side. Someone who has been in twelve times in two months is a regular. On the twelfth visit, the system sends them a referral code and a plain line about bringing a friend to a class. The code is tracked in a Google Sheet, so when the friend signs up the owner can see who sent them and apply whatever the offer is.
Both lists refresh every night from the booking data. Nobody keeps count by hand. Anyone who complained last week is skipped, because those names are flagged.
This is the kind of thing we build. It runs in your own booking system and your own Google account. How many of your regulars have you ever asked?