Big trip

Sac west? Wont that put you in the Pacific? I think you mean east dont you??

In Nevada take Hwy US 50, that will bring you thru Great Basin NP and it has a cave. You can pick up 50 off I-80, in Wadsworth NV just past Reno. 50 in Nevada is called the loneliest road. If you like dinosaur digs then you can visit Berlin-Ichthyosaur State Park via NV 361 east of Fallon.

Park Link

They also have a ghost town and a mine tour.

What sized rigs? Do you have toads? Are you looking for FHU? Do you like to hike or just sightsee from the vehicle? Do you have a month or two months? A little more information will give you much better input.

Another vote for US 50 across NV. If we're heading to CA, it's the route we take.

Include a stop in Page, AZ for Antelope Canyon, Glen Canyon dam, Horseshoe Bend overlook, etc.

Sept/Oct is a perfect time for this trip. Those areas are all favorites of ours. However, traveling with 5 rigs might be a problem if you all want to stay close to each other.

Page, AZ: We enjoyed a flat water raft trip through Colorado River Discovery.
Also Antelope slot canyon.

Along with Bryce and Zion you should include Canyonlands NP. Also driving over the Hoover dam is cool. Plenty of time to plan and make reservations for rvs. Canyonlands is no reservations and first come basis.

For Canyonlands a great place to stay is Dead Horse Point State Park overlooking the canyon.

Good choice from 2gypsies. Dead Horse is pretty centrally located to lots of cool stuff. Check for length restrictions.