Irvine has very nice weather, always in 70s and very clean.
Irvine area are quite flat, so it should be OK for earthquake. San Andreas Fault is quite far from Irvine. And they said all the new house built after 1994 in LA area are pretty safe for earthquake. They changed building law at 1994.
They are a lot activities for kids in Irvine. It's just 10 min drive to Newport Beach.