It's important to keep in mind your goal for the trip. If you're packing your family into an RV and driving somewhere far away, you're going to be dealing with a lot of chaos -- some of it normal stuff, some of it specific to being crammed into a tight space -- and a clear goal is a good way to keep your head on straight. Nobody wants to remember a trip where you yelled the whole time, so it's important to be clear-headed about where you're going and why.
But it's equally important to be realistic about your children's behavior and needs. While a disciplined and well-behaved family is everybody's goal, nobody actually achieves it. There will always be miscommunications, grumpy days, boredom and rivalries complicating things. For most of us, this is only intensified by the close quarters and sometimes lifeless landscape that we're crossing on our journey.
It's important to be honest with yourself, and factor in those little upsets that make family life so exciting. While it's nice to hope for the best, asking the impossible from your family is asking a lot of yourself, as well. Nothing ever goes perfectly smoothly, but thinking seriously about how your family is going to interact in the space you've given them is a great way to head problems off before they present themselves.