If you avoid buying soda, candy and chips then your children won't have them available to eat. Be sure to plan for snacks, too. Have foods available that children can choose from to eat for snacks. And, plan times for meals and snacks. The child's job in the feeding relationship is to decide if they eat and how much they will eat.
Appetites vary from day to day with adults and with children.
So, if a child eats less one day it is not a problem. Get your child involved in planning meals and cooking and their interest in food will improve. Child size portions are also important. Start with smaller servings and let your child ask for more. School-age children eat a limited number of foods initially, but will gradually increase the number of foods they eat.