I'll be entering China in a few months from Ha'noi, Vietnam. We will have approximately 30 days (the full length of our Visa). Can someone recommend a travel path through China? Would be nice if you have tips on places to stop and see. Some criteria:

• Entering from Ha'noi. I imagine this means starting our trip in Nanning.
• Want to see Hong Kong and Macao, which means heading towards Guangzhou before going any further north. (Don't worry, we'll have double entry visas planned already)
• Nature/hiking/etc aren't really our thing but enjoy more social activities (weird foods, awesome museums, etc)
• Shanghai is a must. Beijing is a must.
• Want to end close to S. Korea, since that's our next destination.
  
• No planes, if possible, except when going to Korea. Ferry would be better, since it's likely going to be cheapest.

Does anyone have any recommendations for paths through China and important things to see?