I want to go out to play and talk about it, but I don't want others to think that I am showing off. How should I write the content?

Write in a very peaceful tone, and don't write about it with any ostentation, such as where you went to play today, the scenery was really good and you had a good time. Then attach a landscape photo. Don't deliberately show off, otherwise it will become a pretence. People who envy you will envy it without pretending to be forced. Even those who don't envy you think you are pretending to be forced.