Belair National Park is a great place for a picnic. Out between trees, you'll find a large pond, which has picnic benches and BBQ shelters. There are many ducks that will greet you, and your food, and you may see some kangaroos hopping about while you walk around the park.
It is beautiful scenery, so take a camera and capture all the bright colours of the flowers, green grass, and even moss on trees.
This is a fantastic place to also take the children. They will have fun exploring along the rocky paths within the trees and beautiful nature, down in the fort that was built many years ago, and even feed the ducks and birds in the pond while the parents cook the BBQ.
You can even go to the State Flora Nursery and buy beautiful native plants and flowers, from Sturt Desert Pea to Kangaroo Paw.