Children usually do not eat vegetables because of how they look. E.g.: cauliflower, broccoli, brinjal, etc. If they are not able to see the vegetables, they will not realize that they are present in their food.
The sneakiest way is to make a "chilla", "paratha" or "pakoda"
1. Whichever vegetables you want them to eat, just crush them in a blender and prepare a dough by adding flour. Make parathas and they will not even realize that they have eaten vegetables!
2. Another way is to crush the vegetables and add besan or gram flour to make a batter for" chilla". If you keep the batter a little thick you can make "pakodas" and voila! another way to add vegetables in your child's food.