Ditto what Bowlegs said, except I wear shorts and let the dirt tan act as SPF for my legs.
Also bring a bandana (or get one at the Kickoff if you’re going) Bandanas wrapped around the forehead are always good to prevent sweat (and sunscreen) from dripping into the eyes.
If your friends backpack rides off the back a little that will help a lot with ventilation and keeping dry. If you’re used to East Coast hiking remember, there is very little humidity in the desert so even if you are sweating a lot, just go sit somewhere and dry out. It doesn’t take very long.
Also the desert is not always hot. Mornings are usually cool and pleasant for hiking. And it can get quite cold at night. The trail gets up over 9000 feet in a couple of places so make sure that you’re prepared for some chilly nights. Feel free to email me with any other questions. Happy hiking!
Garrett