We've done the autotrain down to FL every year since DS was born. It was a totally different experience to our other long distance Amtrak trips. You get on the train at about 3.30 and DS goes to sleep at about 7.30. During that time we have dinner, watch a DVD, read some books. Next thing you know it's breakfast and the train gets in at about 9.30.
The food isn't too bad and the staff is friendly.

Have a great trip!

Good luck OP. Have a great time!