We have a similar issue, so we freeze what food we can and put it in the freezer. Then we freeze some water bottles, and put them in the refrigerator section with the food we need to keep cool. Then we start the refrigerator just as we pull out of the driveway. The frozen water bottles keep things cool until the fridge comes down to temperature, and we drink the water. We've been doing it that way for the last 8 years and works fine for us.
It would be nice if we could start it ahead of time, but c'est la vie. We bought a 5th wheel with a refrigerator so we wouldn't have to hassle with coolers, and we intend to keep it that way.