Looks like we are going from Chicago to LA.
Have you heard of this train service:
Pullman Rail Journeys? They have a very special train that does overnight trips from Chicago to New Orleans.
Anyway, I take Amtrak pretty frequently, from Washington DC to NY and cities in Virginia and West Virginia.
I did the auto train from Orlando to DC for the first time this summer.
I've had a Bedroom and Roomette on Viewliner trains, and family bedroom on a Superliner (auto train). I can't imagine doing an overnight trip in coach. Think of the crying babies, hard-of-hearing folks, flatulence, and snoring that could keep you up, let alone the swaying of the train and the train horn.
Throw in that Amtrak is government owned and is less successful than the postal service, and you can set the appropriate level of expectations for the experience. The food is lowest-bidder microwave heatable frozen entrees. The schedule is more of an aspiration, and its not unusual for the long-distance trains to be running 4, 8, or 12+ hours late.
That all being said, the views can be awesome, its a great way to go if everything works right, and the experience can be unique.
On the other hand, I used to have a dream of doing a long distance overnight trip out west like the one you're planning. Then I actually did an overnight on Amtrak, and I'm not so sure. It was tough to sleep. And no matter how awesome the view is, if you miss an entire night's sleep, you don't really care about the outside world. That being said, I'm planning to do an overnight on Amtrak again next summer on the auto train, but this time with a sleep aid and no kids. If I don't sleep better on that trip, I'm going to abandon the idea of a exotic train trip on Amtrak, and try it someplace where the train system is meant for passengers, like in Europe or Asia.