There is marvelous scenery and fishing to be had most years out here in the West, but I recommend you put that trip off to a later year. The scenery will always be there, but the low snow pack we've had so far suggests this will be a poor year for trout fishing.
I suggest you stay East this year. Given your available time, the age of your sons, and your budget, maybe consider a trip up to DC and Virginia. I did a trip with my family to that area when I was about your sons' ages. Williamsburg, the great DC museums, Mount Vernon, Monticello, etc. really impressed me. And I had a chance to learn things about American history.
Cap it off with a 1-2 night stay at Meadow Lane if your budget can handle it. http://www.meadowlanecottages.com/
Upscale rustic cabins with farm things the kids might enjoy. Over 2 miles of heavily trout-stocked private moving water. They are under new management this year so you will have to pay a daily rod fee. But I would not be surprised if they would waive that for your sons, even if all of them catch and release some fish with fatherly guidance.
There is also some very impressive mountan scenery (especially by Mississippi standards) between Charlottesville and Meadow Lane. Trust me --I've been to all 3 places.
I have no financial interest in Meadow Lane. I'm just a happy customer of theirs.
As an empty nester father of three sons, I envy you this trip!