It all depends with the planning on what your exact journey will be like. As we had many farms and a long time to play with, I contacted all the farms early on and booked dates with them, so we had a sort of loose schedule for security. It didn't always work out as planned, and I often called ahead to the next farm to ask if we could come several weeks too early or too late etc, but at least we had already had good contact so there was never any problems. Other than that it was all about planning kit and other activities