Best way to winterize yet still use unit in winter?

Guys, we use water simply for washing dishes, and bathroom, and shower. Nothing else - we drink bottled water. Would you think we'd be okay to just leave it winterized? And simply dump gray/black when leaving the campground and add AF to both tanks upon return to storage?

EDIT: Side note, don't let the south fool you. We get below freezing very often. We thaw out during the day, but we freeze nearly every night. And 8 days of snow last year. Whoo hoo.