San Simeon to Yosemite: CA-1 to Cambria, CA-46 to Paso Robles, CA-46 to CA-41, CA-41 through Fresno to Yosemite. Depending on what time you get to Yosemite, you can spend a night in Oakhurst or proceed into the park. You are looking at about a 5 to 6 hour drive.
DV to GC: CA-190 out the east entrance to CA-127, turn right, then an immediate left on Stateline Road to NV-160 in Pahrump. NV-160 to I-15, 1 mile north to I-215 to I-515 to US-93, cross Hoover Dam. US-93 to Kingman, I-40 to Williams, AZ-64 to GC. This is about a 9 hour drive, you can stay in Williams or Tusayan (expensive) or in the park.