Are they going to Northern or Southern CA? We drove 80 once. I actually got car sick for the first time somewhere in the salt flats. They have signs of driver fatique. I am one that loves to see new places but this was quite boring to me and lonely stretches. We preferred I40. Check if the cell phone has coverage. We switched to AT and T because they had coverage through bare areas. (I only drove 80 from Aurora CO up and west)
Reno would have cheap places to stay (the casinos) if they are over 21. We joined Circus Circus club and can get a room for $29 a night. We always take 50/50 mix of antifreeze/coolant, stop leak, quart of oil and an extra belt (our car had that serpentine belt) ahd jumper cables. We found an old hard suitcase the size of an overnight bag at a yard sale and it's all packed in there. We were charged $150 for a $20 belt once in AZ and that was the end of that. We take a small ice chest with a couple of waters, soda and snacks. Don't forget, no fruit can go into CA so if you have some, it has to be eaten.
If they have time, it's a nice drive from Reno to Lake Tahoe and then come down Hwy 50 to Sacramento. 50 will meet back up with 80 in Sacramento. If I had my choice, I'd spend the night in Tahoe vs Reno but it's more expensive than Reno. Sacramento is 2 hours from Tahoe/Reno. As a previous poster said, there is a rest stop on 80 from Reno to Sacramento but none on 50 to Sacramento. Another plus going 50 from Tahoe to Sacramento is 80 is horrible right now (if you look at a map, Longview Drive to Northgate in the Sacramento area). They just switched to the west bound lanes to do construction.
http://www.dot.ca.gov/dist3/80AcrossTheTop/ (this shows a picture and it's not fun if it's between 4-6pm). If you are in that center thing they created, you can't exit for about 10 miles. You can't get out of that lane until the opening 10 miles later. It's the ugliest thing I've ever seen of any construction on a freeway. Before 4 and after 6 is ok.
There is a rest stop toward Vallejo getting closer to San Francisco.