Another vote for flying vs. driving. Half or more of your trip just staring at the windshield. And driving your rig around LA wouldn't be fun at all. Maybe you've driven in Calgary or Vancouver but neither of those hold a candle to the mayhem and madness of driving in and around L.A.
Besides, there's a whole lotta other things to do in and around the area once you get there. And San Diego also has great attractions. Head to the beach, Seaworld, the San Diego Zoo (world class). Spend your time doing things your kids will remember other than spending days in the coach.