I visited China with JY in 2011.
All hotels we used and the boat for the Yangtze cruise accepted credit cards. I didn't need to use my credit card elsewhere but others who wished to buy expensive items did without problem.
The need for Chinese currency depends on your personal needs and how much you want to buy. But all extras at hotels I paid using credit card and day to day needs were relatively modest as all meals were included. The tour manager helped a lot to enable us to obtain Chinese currency and to change back to pounds at the end. It's a good idea to make sure any notes you do take are in pristine condition so that exchanges do not refuse them.
I found no need for US Dollars but they may be easier to exchange than Sterling
Hope this is of some help with your preparations to visit this truly fascinating country.