Go on a picnic就是说你参加了一个聚餐,没有特别的意思,最常见. go for a picnic有时候带一点细微的放弃了其他活动转而去picnic的意思,或者一定要去的意思. go for a picnic在美国英语中是一个习惯用法,而且go for之后还可以跟其他的表示户外活动的名词搭配. go on a picnic这个短语中真正属于习惯用法的是on跟后面表示旅游...
A picnic plan The winter holiday is coming.My family and I are going to go on a picnic. First,we going to the supermarket buy some food and drink.Then go on a picnic. We are going to picnic at sea...