How to manage inactive softeners is always a problem.

Most important, the softener can not FREEZE.

Without knowing what softener you have if the softener is an on demand electronic unit it may have a day override so emptying the brine tank will not stop regenerations.

You'd need to shut off the water and pull the plug to stop regenerations then bypass the softener after relieving the internal water pressure. I'd empty the brine tank and toss the salt.

You should be shutting off the water when you're gone for an extended time anyway.

Since you have iron, are you routinely using Iron Out or a similar product?