What a great time the children had in the park.(同义句改写）
（What）（fun） the children had in the park.
这些孩子们在公园玩得多开心啊!
have fun,玩得开心.这边的fun是名词还是形容词？funny是形容词，fun是名词，乐趣。所以用what作为感叹词。