FLHTCI,
I am also in SE MI (like Old Wizard). Our climate is not that different than MA. I know, I am a refugee from the east coast Megeapolis. If you keep the temperature in the coach comfortable, there is no reason to drain the tanks.
Be sure to have enough LP for heat in case you get stopped. but other than that there is little to worry about. Yes, you might like to leave cabinets that contain water lines open.
If you should find an open cramp ground to stop at that might freeze, fill the potable tank and run from that. If you have to get out the potable water hose and are not sure it is going to stay warm, drain it before you stow it. If it gets to freeze, it is a problem.
Unless you run a great deal of water, the black tank will not freeze, but the gray can. That can often be (capriciously) dumped into a storm sewer.
Matt