Question
our house is at the top of a hill. Several CA live oaks on our property, near the bottom of the hill, are now over 50 feet tall and starting to block our view. What is the best way to control the height of these trees?

Answer
I would recommend you consult an ISA certified local arborist (ISA stands for International Society of Arboriculture).  They can be searched for at:

http://www.treesaregood.com/findtreeservices/FindTreeCareService.aspx

Specific information about the California Live Oak (Quercus agrifolia) and its unique habits:

http://www.californiaoaks.org/ExtAssets/oakcaresec.pdf

Their roots are more temperamental than the branches, but it is best to get a local expert's opinion.

Hope it helps.  ~M