I will be attending my son's wedding to a Chinese woman in a few weeks. I am from the US.

Hello Jill, don't be nervous! The girls parents will be easy-going. Most parents won't be picky, as long as they are content with the future son-in-law. For gifts, you can prepare a shawl for her mother and a necktie for her father. This is just for reference. It is also fine to bring some tea, wine and nourishment. If you buy the specialties of your country, they will be glad.

You can just wear usual garments. Don't too casual nor too formal.