I made sure to feed my children 20000 calories a day
That does sound kind of sad. I hope you are doing this for their best interests?
I just want to make sure that they are eating enough.
It is wrong to feed kids too much food because their health could be affected. If they get fat they might end up with diabetes.
Gym is a great way to burn calories.
You could also work on portion control with them. It is better to teach them that young so that they do not have to learn how to when they are older.