Shuttle Buses Payment Methods, Cash Accepted?

Going to Zhangjiajie National Forest Park and Wulong Karst.

There are shuttle buses that can take you around and you pay once you get on. From videos, I've mostly seen WeChat payment being used.

My senior parents don't have a phone or their own WeChat account. Can you pay with exact cash? Or, can I scan the QR code twice to pay for them?