Legal Question in Criminal Law in Alabama

The restaurant can probably fire all three workers, unless some or all of them have a contract (including possibly a union contract) which limits the restaurant's ability to fire them. An internal corporate policy and/or an employee handbook might also give them a level of job security.

The restaurant is free to ask the local prosecutor to bring charges against all three employees, but whether to do so is the prosecutor's decision. The employer likewise can't decide which, if any, of them will be arrested. That is a decision for the police to make. Both the prosecutor and the police will act only where there is evidence that a particular person committed a crime. They won't arrest multiple people merely because it seems likely that one of them is guilty, especially over a small crime like this.

It is possible for three people to commit a crime jointly. If there is evidence that this is what happened, then all three of the fired employees could be in trouble with the law. That seems unlikely, but without more information I can't say one way or the other.