No it’s not unrealistic, success is determined by the skills, equipment and individuals involved. Circumstances and conditions dictate the environment. I can build a shelter if need be, make use of an unoccupied building or sleep under the stars. Primitive societies lived in cold climates, jungles and deserts thousands of years without any modern inventions. Certainly it can be done now if required. Where your family is young, mine is all adults. Everyone has their own set of parameters to work out the best they can. What happens if you are forced to leave the RV?