single or multiple entry visa required?

We are travelling to China on a cruise ship with three stops at different ports over a period of a week being Shanghai, Beijing and Dalian (without entering any other countries between each port).
I have been advised by a service agency that a single entry would be sufficient under these circumstances. Also that a 'group visa' would be sufficient as there two of us travelling.
Is there any way to get an official ruling on this. The Chinese Consulate here wasn't able to advise me.