Will it be difficult to procure vegetarian food in Shantou?

No, there are a lot of vegetarian restaurants in that city. Here is some recommendations.

Xinmeiyuan Yuantong Vegetarian Restaurant, located at North Huashan Road, Jinping District.
Lianhua Vegetarain Restaurant, No. 33 of Haibin Road.
Yangxinzhai Vegetarain Restaurant, located at South Jinlong Road.

Hope helpful.

Thank you so much for the information Lily :-) I am relieved that I don't have to go without food the week I'm in the city :-D