Ask Mr. Smarty Plants

Mr. Smarty Plants feels that the best bet for deciduous trees native to your area would be Quercus kelloggii (California black oak), Quercus douglasii (Blue oak), Quercus lobata (Valley oak), or Acer macrophyllum (Bigleaf maple).  The oaks all grow rather slowly, so that it would take many years for them to surpass the 20 foot height you prefer.  You will see by clicking on the underlined names that the Valley oak ultimately grows much taller than the other two species.  The growth rate of the Bigtooth maple is  considerably greater than that of the oaks.The maple naturally grows in moist valleys, and you would need to provide it with more water than needed for the oaks.  I am assuming that your homestead is in a dry area typical of your part of California.

This web site provides information about the care of oaks.  They are generally free of disease and insect problems.  But Sudden Oak Death has been found to affect some California black oak trees.  The Bigleaf maple is relatively resistant to disease.

The Lady Bird Johnson Wildflower Center Image Gallery does not contain photos of these trees, but I incluce photos from the Internet of California black oak, Blue oak, Valley oak, and Bigleaf Maple.  Any of these trees should be available at one of your local plant nurseries.  Winter is the least stressful season for tree planting.