There are three places to recommend for a one-day picnic:
1- Maluoshan Wilderness Park
The mountain is not high, and it can reach the top in ten minutes. The environment on the mountain is primitive, with streams and waterfalls.
2- Yangmeikeng Valley Valley
Go to Luzui Mountain Villa. It S suitable for self-driving/cycling/renting a car/speedboat. The water quality is very clean. You can play in the sea or barbecue and camp at night.
3- Shenzhen Bay Park
In the evening, watch seabirds and blow the sea breeze. The grass is wide and cool, so you can bring your own picnic mat.