Chinese guides? Do you mean you join a tour and there are chinese guides of the travel agency to pick you up? If yes, i think it is not necessary to bring them anything. If the chinese guides refers to the the teachers in the school where you are going to teach, you can bring some american-featured presents. Actually, they will be quite happy for whatever presents you give to them. Chinese people are all warm-hearted and kind. Enjoy your teaching in China!