K.N.
You may consider giving them something like Benedryl to help them sleep. It would make for a more pleasant drive (the driver can focus better as well) and they would be well-rested and less crabby when you get there.
(In my defense for those that disagree with this: I've never done this myself and I've always avoided any medications for my family unless absolutely necessary. But I have heard of others that have done this and, in some circumstances, it may prove to be the best option.)