We are planning a trip in late October early November - arriving in San Francisco (from London, UK). We are a family of two adults and three children (12, 7 and 3) and don't want to try to do som uch that we spend all of our two week vaccation driving.
I'm thinking of a couple of days in SF, then drive to Yosemite, then down to Las Vegas and Grand canyon, then across to the Pacific Coast and back up to SF.

Is this too much?
Can anyone suggest a scenic itinerary with a misture of things for kids to see and do?
Also, any tips for nice places to stay en route?
Finally - are there any legal requirements for the three year old - does she need a separate car seat for example?

Thanks for any advice you can give us.