Great plan! I'm envious!
Suggestions: ride the Texas Eagle #22 from Dallas to St. Louis ( overnight), catch the Missouri River Runner to Kansas City ( there are 2 Trains, a morning train #311 and evening train. #313) You have a chouce of spending the day in St Louis or evening in Kansas City!
You then catch the Southwest Chief, #3 from Kansas City @_1030pm to either Flagstaff or Williams Junction,Arizona. Its an overnight and day trip on the Chief, arrives Flagstaff @ 850pm, Williams Jct @ 930pm.
Flagstaff is a real town with hotels, airport,stores, rent cars etc. Williams Junction is a platform where a Van meets you and takes you to a Hotel @ the Grand Canyon. You can ride the Grand Canyon Railroad also but IRS a daytime activity and not really worth it! You do not want to do this in the Summer, it gets very crowded and Hot @ the Canyon then! Spring or Fall is the Best time, its actually cold with some snow in the Winter!
After the Canyon visit ( allow @ least 2 days/2 nights, it's worth it)you take the van from the hotel back to Williams Jct to catch the Chief to LAX ( arrives 933pm or if you've taken a rent car and stayed in Flagstaff @851pm.)
You'll arrive into LA ( Union Station/LAX)around 815am, then catch an Amtrak Bus to Bakersfield, change to a San Joaquin Train to Fresno
where you can pick up a Rent Car to visit Sequoia and Kings Canyon National Parks!
After returning to Fresno you catch a San Joaquin Train to Merced where a Chartered Amtrak Bus will take you to Yosemite.
After your visit to Yosemite, catch a San Joaquin train to Emeryville,get a Rent car and spend the night. ( Emeryville is where the Bay Bridge goes across the Bay to San Francisco).
Drive up I-80 ( Freeway to Sacramento) to the cutoff for Napa Valley ! There are usually 2 Napa Valley Wine Trains a day, a Lunch and a Dinner run!Napa and Sonoma Valleys are very expensive, you might want to consider staying in Petaluma, Santa Rosa,Fairfield or Suisun City in a cheaper hotel/motel.
When you're visit in Napa is complete, drive back to Emeryville, catch the California Zephyr #6 @915am for Galesburg, Illinois ( two days and nights) where you'll catch an Am Van to Springfield Illinois to catch the Texas Eagle #21 for Dallas, an overnight trip arriving in Dallas about Noon the next day!
If you want to come home a different way you could catch the Coast Starlight#11 in Emeryville to LAX, then the Sunset Ltd./Texas Eagle #422 ( a two night/2 day trip) to Dallas which only runs 3 days a week!! The California Zephyr has lots better scenery than the Sunset/ Texas Eagle!
Sorry this is so long! There are lots of people here who xN help with the Park info and you can Google old threads here in AU that discuss these subjects!