Háizimen zài jiāniánhuáhuì shàng wán de hěn kāixīn.
The children had a great time at the carnival.
Tips
usage
嘉年华会 is a longer form of 嘉年华 (jiāniánhuá), which is itself a phonetic borrowing from the English word carnival. The 会 adds the sense of a gathering or event.
