4 days Huangshan and HongCun

Generally speaking, your plan can be good. Kindly suggetion is that Hongcun is a little far from the airport, so you had better hurry up to catch the transport.
Many hotels in Hongcun are simple and quiet. Amng them, Huazhong Hotel and Xiaotaoyuan Hostel can be taken in your list. If you plan to have a rest on the mountain (Xihai Area), you can certanily check in the Xihai Hotel there, which provides good service.
From Hongcun to the mountain scenic area, you can take a direct bus in the local bus station.
Well, as for the transportation from the mountain to the airport, you need go to Tunxi Bus Station first. Then you can take a taxi to the airport.
Have a good trip!