Vegetarianism is a way of life for a vast majority of people in India. It can be a very healthy way of eating, especially if it includes eggs (ovo-vegetarians) and milk products and if the said meals are planned thoughtfully. It is important to include a variety of foods rich in vitamins and minerals, along with proteins, carbohydrates, and essential fatty acids so that nutritional deficiencies do not occur.

The quality of animal protein is superior to that of plant protein as animal protein supplies the body with all the essential amino acids whereas plant protein is deficient in some of these. However, when meals include food from a variety of dietary sources, the diet becomes balanced because the missing amino acids or nutrients from one source get complemented by those from other sources.
A toddler's diet is extremely important. It is vital to his rapid physical growth; general health and well-being; his ability to learn and play; and also his future health. Therefore, extra efforts should be made to ensure that he gets the right types of food.

Milk and Milk Products

Milk (especially the full-cream variety) and milk products are very important for growing children, as they are a good source of calories, calcium, proteins, and vitamin A. These are especially important for vegetarians, as they form one of the major sources of nutrients and proteins from animal sources.
Calcium contributes to the formation and maintenance of bones while Vitamin A is crucial for healthy eyes. A vegetarian child should be given full-cream milk at least for the first five years and then low fat or toned milk can be introduced.
If a child is intolerant to cow's milk, he can be given calcium fortified soya milk.
Milk can also be given to children in the form of Yoghurt (Dahi), Paneer, Cheese, and desserts like Kheer and Custard. Children who are lactose intolerant can tolerate the above milk products.

Eggs

For ovo-vegetarians, eggs serve as an important source of some of the essential nutrients. Eggs are an excellent source of good quality animal protein and provide the body with the all essential amino acids needed for proper growth and development. Other than protein, they also contain essential vitamins (except for Vitamin C) and minerals. 

Fruits and Vegetables

All children should be encouraged to eat at least five portions (500g) of helpings of a variety of fruits and vegetables every day. They provide all the essential vitamins and minerals, dietary fibres and phyto-nutrients needed by the body. It is important to eat a variety of fruits and vegetables because one particular kind may not be rich in all vitamins and minerals. Some sources are rich in a particular nutrient while others may be rich in other nutrients.
Fruits are also especially rich in Vitamins and Minerals and dietary fibres. Whole grains are rich in fibre; vitaminsB complex and E; minerals; proteins, and complex carbohydrates especially the slow releasing kind that provide more sustained energy. 
The proteins in whole grains lack certain essential amino acids required by the body, and should therefore be eaten with pulses, milk, and milk products; to ensure that the intake of all the essential amino acids happens.
When whole grains are processed or polished, they lose a lot of their nutritional value, especially B vitamins. Therefore, it is desirable that you encourage your child to consume whole grain products. Whole grain products also serve as a good source of dietary fibres.

Legumes or Pulses

Legumes or pulses (lentils) are the main sources of proteins for vegetarian children. Although they are a good source for proteins, they (except for soya beans) do not provide all the essential amino acids required for proper growth and development. Therefore, these must be eaten with cereals and/or milk products. Besides proteins, pulses also provide complex carbohydrates, vitamins (especially the B vitamins), minerals and dietary fibres. Soya beans do contain all the essential amino acids needed by the body as also useful amounts of iron and calcium. 

Nuts and Seeds

Nuts and seeds are high in calories and are nutrient dense. They are rich in proteins, some of the vitamins and minerals, essential fatty acids, and fibres.
Almonds, cashews, pecans, pistachios, macadamias and walnuts are especially rich in some needed nutrients as well as in polyunsaturated fatty acids. As far as the seeds are concerned, sunflower, pumpkin, flax and sesame are the best. 
Always give ground nuts to avoid choking especially if your child is under the age of 5 years. Salted nuts are likely to have higher sodium content, so it is better to buy the unsalted versions.

Fats and Oils

Fats and oils are an important source of energy and essential fatty acids. They help the body to absorb fat soluble vitamins A, D, E and K.
Intake of saturated fats (whole cream milk and butter) along with hydrogenated (Vanaspati Ghee) and trans-fats should be restricted because they raise the level of LDL cholesterol that can cause health related problems. Although oils and fats should be generally restricted, they should not be restricted in under-5 or preschool children as they are important for the proper development of the brain and other vital organs. Omega-3 fatty acids (especially DHA) is essential for aiding brain development and should be made a part of your pre-schoolers' diet as brain development is maximum till the age of 5 years.
It is possible for children to get adequate nutrition from a vegetarian diet as long as the diet is well balanced and includes all the essential nutrients that a growing child needs.