Travel to China by cruiseship

I will be emabarking on a cruise in Hong Kong on April 11, 2013. I'm aware I don't need a visa for HK but need one for China. The ship will be at Tianjin port for 3 days and we will travel to Beijing for a 3 day/2 night private tour. We will then cruise to Baoshan port for Shanghai on April 25, 2013. We will do a one day tour in Shanghai and get back on the ship as it continues travel to Japan and ultimately Alaska. I will be applying in Los Angeles. Do I need a multiple entry or double entry visa? How far in advance should I apply? Will I need more than a copy of air confirmation from LAX to Hong Kong and proof that we're on a cruiseship? We want to do same day service and need to make sure we've got everything necessary with us when we apply .