Attractions in Shantou and nearby city

Hi there, this is my 1st trip to Shantou with my grandpa (80 plus) and a few relative members. I would like to find out on the "Must Visits" in Shantou and how many days should we stay there to be sufficient to look around and if we would like to travel to nearby City for Sightseeing and exploring the local cuisine, where can we go? We have a total of 6 days to spend and we are planning to hire a van. Thank you!