So a fun little update for the future would be to use a feature already availble within Square. To change the pick up time and have it notify the customer.

Sometimes you get busy, more than usual, and making an order can take more time.

In the Order Menu on your Square POS when you click on an order to view the details (when ordered online with Square). The time set for pick by the customer is a hyperlink, if you click on it you can change the time of pickup buy choosing a set of pre-set times by Square or other and choose a specific time.

This is doable before the order is being processed. Once the order has been marked as "in progress" the time can't be changed.