gifts for friend in China

i am going to buy some gifts for my best friends who helped me a lot to take care of my parents, we are really like brothers, we were born the same year, go to the same middle school and high school. Money is not something between us. I do not know what I can buy for them, they are rich. I am thinking to buy wine for them as pure friendship, I have so many friends, I need at least 4-5 bottles. Which way is better? is it buy it in US airport or in Beijing airport for tax free? Should I pay tax if I buy 5 bottles (500ml)?

Any suggestion is greatly appreciated.