We winter camped and hunted for years in cold country. Just blow out the water system and used bottled water, kept the heat on low, gen to charge batteries. Some pink anti freeze in holding tanks.
If traveling the engine should keep the battery up, so run the heat. A small quite gen will keep them up at night. Or get a Passport card and stay in parks overnight.
04 Horizon QD, 12 Ford Flex, Excalibar, Brake-Pro, ,, Winter Texan, RVin! since 1974
Norm, Donna & Tinker Kat 74 MGB-GT, 75 MGB, 01 Z3
Life is a Timed Event, you only get One Go Around!