Living in Ottawa, Ontario makes me very much aware of freezing temperatures.
For the winter storage of our sailing boat, I always run plumbing anti-freeze through the pumps and lines.
When we bring the trailer back to Ontario in April, I do the same before we use it mid November for the trip to Arizona. We do't use anything but the toilet and bottles of water (filled at home) until we get to about Nashville.
I'm not sure about blowing air through a system. Will it clear out the liquid in pumps ?
One winter we turned off the water supply and drained our house lines of water. When we got back in April, two sink units had to be replaced as the inaccessible rubber washers inside the taps had dried out completely. Now we turn the mains water off, but leave the water in the lines. No problems. We leave the house at 15 deg centigrade (53 F).