Please check this text

This is my description of the picture (for children).
I can see six children in the picture. They are in the countryside. They are swimming in the lake, playing ball, watering vegetables in the garden, picking apples. I think they are staying in the countryside for one week. They are happy because they are all smiling. They are in a good mood. I can feel their happiness. They are having a good time!
Is this text grammatically correct? I mean articles and etc. And can I use Present Continious Tense describing the picture with childrens' actions? Or better use Present simple, for example: They swim, play ball and etc? Thank you!