Managers should not undermine their employees. This is a bad decision from every possible standpoint. If you continually undermine your employees when they ask customers to follow rules that you or the corporation you represent have invented (usually to promote profit...which is after all why they hired you as a manager...because they thought you could help the store make a profit), the employees will no longer be able to enforce those rules at all.
Customers that have had a rule broken once for them (a paid service for free, etc) will continue to expect that same treatment in the future. This is a fact, and it is really unfair to expect them to act any other way. If employees know that when a customer challenges something they will immediately get their way, that employee is not going to waste their time and energy enforcing unpopular policies.
Also, it is not a "best practice" to wait until the first day of a given week to give employees their schedule for that same week....ah well.