Why not modify the policy, to wit:
When one or both parents cross the border illegally with their children, they should be offered the choice:
Option 1: "separation", insofar as it the current policy mandates
or
Option 2: They can remain with their children, but only by returning to the other side of the border (or if not Mexican, their country of origin) immediately. If they agree, all records of their having crossed illegally [for this attempt] will be expunged from the record, and they will then be able to apply for legal admittance through the American embassy in their country of origin.
If they choose option 2, and they are not from Mexico, they will be provided return transportation free back to their country of origin...