Thanks for all the advice.
We've recently did a day trip with the kids to Utah, but it didn't work out too well.
Emily (6) is fairly resilient, and I can imagine taking her on long trip without much trouble. Kyle (3), on the other hand, is very sensitive and has had some sensory development issues. When he gets tired or upset, he usually loses it and will scream and cry continuously -- it takes him a long time to calm down even if we try to help him. For example, if he sees a bug, he may scream for 20 minutes straight. If you look at him a certain way, he'll scream. If you ask him to do something, he'll scream. When we travel with him, he spends a good part of the trip screaming at the top of his lungs because of his sensitivity and sensory issues.
He's gradually getting better and will probably outgrow this phase within the next year or two. Once that happens it will make traveling with the kids a lot easier.
All kids are unique. Kyle is in preschool now, and the positive side of his being so sensitive is that he's extremely emotionally aware of what others are feeling. He goes around hugging the other kids regularly, his teachers adore him, and he already has a "girlfriend." That quality will serve him well once he learns to manage his own emotions a little better.
Kid Kennel was just a joke by the way.
