Hello and welcome to RTA !

There should be no need to pre-book accomodation so I would recommend checking the weather forecasts and road conditions before you depart. All things being OK I would be tempted in going up I15 all the way to I70, one of the [probably thee] most scenic Interstates of them all.

You should have quite a relaxed trip but you will be on the road for 9-10 hours a day to complete the journey in 5 days, despite what a mapping program might tell you. They do not allow for the need to rest, eat, fill with gas or account for posiible construction and congestion delays. Figure on 550 -600 miles to take 10 hours with said breaks and you won't go far wrong. Treat the journey as a marathon and not a sprint and don't get tempted to push to hard at the beginning of your journey or fatigue could set in for the second half.

Have a safe trip.