Babies in diapers when you travel means a lot of stuff to bring, and potential surprises along the way.
When the kids were young (age 3, 2, and 10 months), we decided to go visit relatives in Toronto. That meant a really long drive, with a stop in Montreal, to visit my mom and stay overnight. Because the youngest one was only 11 months old, we had someone babysit him at home. We knew he would not enjoy the trip, and it would have made it even harder for us.