Hi! We did this about 3 years ago with three kids.
The coach, was fine. And my kids considered it an "adventure"
Here is the down side...
Some people are not very "considerate of others"
We had one family who let their kids run wild on train and when 90% of us were trying to sleep, these kids kept running up and down the aisle and opening closing the doors between cars... not much sleep to be had.
The seats were ok.. you definately want to bring pillows.
The waiting to get your car back is not a short one. Unless it's a little car.. sometimes you get lucky.
The food was nothing to write home about.. we had bought snacks as well. I'd actually consider doing again.. but my husband would rather drive.
Please feel free to ask any other questions.
Kat