Looking at my AAA maps of AZ, NV and OR I would go from Prescott north west on AZ Hwy69 to #89 and then north to I40 and then west to Kingman, AZ and then take AZ Hwy 93 north into Las Vegas ,NV to Hwy 95 and take that north to Fallon, NV, I would take NV #50 west to I 80 and take it into Reno NV to Hwy395 , go north on 395 to Susanville, CA . There are two ways from there to get into Oregon, one is take CA 139 north to Klamath Falls, OR and then north on OR Hwy 97 or go west out of Susanville to CA#89 and take it north to ! 5 and take it north up to Eugene, OR and take Hwy99W to Hwy 20 and take it west to Newport.
If they are going into Klamath Falls from Susanville, CA , take OR Hwy 97out of Klamath Falls north to OR #58, take it into Eugene and then take Hwy 99W up to Hwy 20 west into Newport This is the scenic route with less traffic and stops also
IHTHs
EDITED,: Caution them on NOT USING there smart phone GPS based navigation for short cuts , especially on this trip
My grandson drove form Florida to here in Bend,OR, he called me from American falls, ID and ask me how to get from I84 to Bend, I gave him instruction exact instructions from Burns, OR when he drove West on OR Hwy 20 from Burns to the east side of Bend. He ended up using his phone directions about 8 mile east of town at night and ended up on a dirt road which did ended up getting him to a paved road in Bend. it was in the late spring and there was no wet or bad roads he had to drive on, we have had several out of state people get lost and one died form getting stuck in the mountains in a snow bank and tried to walk out, DON'T DO THAT No short cuts Stay on the pavement