Now you need to structure your argument:
1) Children should exercise everyday because it is good for their health. It is good for children to be healthy by exercising as often as possible.
2) A reason why you need to exercise and to be fit, is if you are in a sports team you will be ready to compete for the school or team. Children who are fit won’t get tired as easily. Being part of a sports team is a great way to get fit and have fun at the same time. You also get to develop your skills in that sport.
3) I believe that you can get fit by doing exercising skills. For example running up and down stairs, riding a bike up a mountain, skipping, squats, lunges etc. These exercising skills will help you get fit and healthy.
4) If there is an event coming up and you are fit you will do good, but if you are unfit you might run out of breath and be tired. It is good to be fit because it does really help whenever you play sports or just doing anything that requires running, squats etc.
5) The differences between a fit person and an unfit person is really clear. A fit person can run 2 laps around a field but, an unfit person will run but will get tired faster than the fit person.
6) I agree that children do need to exercise because as I said, it is good for their health. Exercising is not only just good for your health exercising is good for your lungs, heart, muscles, kidneys etc. This concludes the end of my argument for today.