I would try to find a Class C that will work for your family. A Class A is not something you want to drive down Highway 1 or into Santa Cruz.
In your place I would be renting a hotel room and a car for the time you plan to spend in San Francisco (or using their excellent mass transit and walking which is easy enough to do as parking is terrible in most parts of the city and eats up a lot of time). After your time in San Francisco then rent the MH and drive down Hwy 101 to Monterey.
Problem in general is that most places you will not be able to park the Class A motorhome anywhere near where you want to walk and explore. It is like being on a tour bus but you do not have a driver to drop you off and then pick you all up later. Class A owners for the most part tow a small sedan behind the motorhome and use it to get around.
There are Class C motorhomes with slide-outs that provide additional sleeping area at night or eating space for meals. They are much shorter and so can be parked on the street or in public parking lots like a car.
