Winterizing: What to do with humidifiers if turning off the main water valve
I don't see why you would automatically get cracks without a humidifier.

Anyway, I strongly suggest turning off the water - it's far too risky not to. The damage from a leak will be way worse than a crack.

I would do #2: also turn off the humidifier. But: If I were really worried, I'd get a large bucket of water and leave it near a heat vent to warm up and put some water in the air.

Maybe experiment a bit before you leave see how fast it evaporates, and if it's too fast cover it partially. If too slow then put a synthetic very clean (you don't want mold) rag in it attached to something above it (to increase surface area).