Junk foods are full of fats, sugar and even salt which is not good for children. Eating the right foods is the best option if you want a healthy young adults in the future. If you want them to be bright or intelligent then give them nutritional foods like vegetables and fruit with little or enough meat for bones development.
Avoid junk foods as much as possible if you can. Eat fresh fruits and vegetables plus pasta. This way you can be sure of healthy being.