描述节日活动 — 英语阅读题

Read the passage and answer the question. The Mid-Autumn Festival is here. My family are in the park tonight. Look! My parents are sitting under the big tree. They are eating mooncakes and drinking tea. My sister is singing a song about the moon. My little brother and I are playing with a lantern. Everyone is having a good time. Question: What are the writer's parents doing at the Mid-Autumn Festival?