They said they don't want to fly, so that's out. I'm assuming someone in the group has a fear of flying. Flights are pretty cheap, but driving a whole family will be much cheaper (even though everyone will be less happy about it, it's a LONG drive from SF)
Amtrak would work fine, as would any bus service. They do take a long time, but if they won't fly then that's the only remaining option.
If you want to do this on the cheap, the hotels down the street from Disneyland are usually MUCH cheaper, and most of them provide free shuttles to Disneyland. If money is no object, just book one of the Disneyland resorts; then the kids can get into the park an hour before it opens.
That said, I'm going to Six Flags on Sunday, the superior amusement park (40 min to Disneyland, 1.5 hr to Six Flags, I'll choose Six Flags almost every time - better rides, cheaper tickets)