I envy you for having 1 acre of land.
As others have said GSD are very
territorial, protective and easly trained.
Even though it will not stop the dogs from
being territorial/protective,
I also think obedience training is a wonderful idea.
I was wondering if it is possible for you to
fence/gate off the section of the property from
the driveway to the patio?
That way when you are expecting company, you can
always close that section off and not worry
about your company and the dogs.
Just a thought. : )