You could certainly do what you are proposing. Another way would be to just have the RV antifreeze in the bathroom and pour it into the toilet when you flush. Probably use less of the expensive pink stuff that way.
Are you going to live in the unit during the trip? I'm wondering where the "gl jugs of street water from home" are going to go? If you let it go down the drains, it will freeze unless you keep heat in the unit. Dumping the tanks could be a problem also if the dirty waters freeze. I guess a lot depends on weather you heat the unit during the trip, how cold you are expecting, and is the unit built to withstand winter time use.
Good Luck, Be Safe and Above All, Don't Forget To Have Fun
2006 Fleetwood Discovery 35H, 2014 Honda CR-V, M&G Engineering Braking System