You might also consider an inland route during one leg of your trip south.
The east slope of the mountains along the west coast, gets much lighter
traffic and has some pretty nice areas.  Camping without reserving spots is
not too difficult, if you  are able to get along without the
"Tourist/Motorhome/Phot-op/Campfire Program" style of amenity that many
think of when they go 'camping'.  Many public lands still allow the public
to use them without fees, but be sure to take care of these areas if you do
camp out in an "unstructured" spot like I almost always do.
  There are state parks in California along the coast, but these are almost
always full of reserved campers in mid-summer,  so if you plan on camping in
the more popular parts, you just have to reserve ahead or go "Private" like
to a KOA or other commercial camp area.
  The Oregon coast is very crowded on weekends..unless the gas costs keep
some people home this summer.
  I like to travel using those Topo map Atlas books..DeLorme, etc.  They
have plenty of campsites and points of interest marked on the maps and lots
of small back roads that are interesting alternatives to the main routes..
 Don Hanson