Grand Canyon to Malibu Beach

That's too far a drive for me, but it can be done. I would, and have, headed north at Kingman, Arizona to Las Vegas. It is a very nice mostly divided highway and with the bridge you no longer have to cross the Dam. Then head west on the I-15. Take the I-15 to the 210 West to catch the 405 to Malibu. Mileage wise it is a long drive. If you hit traffic it becomes a very long drive. Sunday from LV to LA can be horrible. If you hit rush hour on the 210 you will crawl for a long way, but the chance is less than the other inbound freeways. The 405 over the Santa Monica Mountains to the coast is usually packed, and often worse than packed. We usually plan on an hour to 1.5 hr drive from our home to LAX, 30 miles away.
Personally, I'd do Grand Canyon to Las Vegas. Enjoy the evening. Then head for the coast early on a weekday morning, reaching the 210 about noon to 1pm.
Enjoy.