Do you mean a bilingual language school, which teaches Mandarin as well? If so, you could find a local international school. If the kids is under 5 years old, there will be many bilingual kindergarten for your choice. Finally, you could employ tutor from a local univeristy.

As I know, there were foreign volunteer at the Panda Reserve before. You could contact with the reserve for details. July will be somewhat hot and wet in Chengdu since summer is coming.