Definitely will be a great trip!
Zion is great (stay to the center of the tunnel!), Bryce and Capital Reef will be spectacular. You will go over the 'hogback' in Capital Reef - 1000 ft drops on both sides, no guard rail or shoulder and a steep grade!
550 in Colorado is no picnic between Ouray, Silverton and Durango - some real high passes. But the scenery is will challenge you to keep your eyes on the road.
Get the rig checked out thoroughly in SD. You have a lot of desolate driving through the square states and you don't want to break down.
Tom and Katharine
'07 Winnebago Tour 40TD, 400hp Cummins
'17 Winnebago View 24V, '02 R-Vision B+
RVing for 20 years & 200,000+ miles