Dad was big on planning and practicing. So he had us practicing starting the summer of 1950, a year before the Big Trip.
The first trial run was a long weekend up the Hudson River to the Catskill Mountains. This was a test of a very specific premise. The plan for the Big Trip was to buy a house trailer and live in it. So we rented one with an option to buy. We didn't like it. Mom didn't like it because it was crowded. Dad didn't like it because pulling it with a passenger sedan was a nightmare. ("Every time we went down a hill, I kept looking to the left expecting it to pass me.") Us kids? I guess we liked it as a novelty -- but it wasn't something we really wanted to do all the time.
A few weeks later, the family did a four-week tour of New England and upstate New York. This time, we did it by car and lived mostly in "cabins". We started with a week in one place, on a farm in the Massachusetts Berkshires. We lived in the guest rooms in the farmhouse; the farm family made extra money boarding guests, and we had the farm experience. We saw Boston, the White Mountains (NH) and the Green Mountains (VT), Ottawa and Toronto in Canada, Niagara Falls, and the Corning Glass Works.
One of my vivid memories is pushing the levers to control the locks at the Welland Canal. That is the waterway bypassing the Falls if you are taking a ship between the Atlantic Ocean and the Great Lakes. Think about how different that was in more innocent (and less litigious) times. Today, a tourist would not be allowed anywhere near the lock control house, much less allowing a nine-year-old to push the levers allowing a couple of lake barges to "lock up" from Ontario to Erie.
This one-monther was a great shakedown cruise for the Big Trip, and it was very successful. There was nothing insurmountable about our traveling together for an extended period, and we all loved the new experiences.