Do we need a visa to visit HK and Shenzhen? We are US citizens and would like to visit .

Peggy, you don't need the entry permit for HK, but you need one for mainland China. Specifically, you need a tourist L type. Before booking your airline tickets and hotel, you can prepare your passport, a filled-out application form, a passport style photo, and a copy of your passport. After you get the tickets and hotel booking, you can start the L type application.