How can we keep track of whether a customer has used their quota in a subscription plan?

[motherpacha]

We are a small cafe and would like to try a membership subscription service which gives 3 (say) all inclusive meals a month for a fixed price. However, short of manual tracking on a spreadsheet, we can’t see a way to track whether a customer has used up their quota for the month. The only very cumbersome thing I’ve thought of so far is to give a subscriber 3 member-specific coupon codes, but I don’t want to put the burden on the customer. Also I don’t think the in-store POS allows one-time use discount codes (as opposed to the online coupons), and I need to make it fool-proof for the baristas ideally.

If anybody knows of an integrated app that might do what we want, or can think of a work-around, I’d really appreciate it. We are trying to develop a more consistent weekday revenue stream in our new location, and really want to try something like this.