How about vegetable purees or smoothies? You can try this smoothie recipe which is delicious and has applesauce and banana as part of the ingredients. The taste of spinach will be subtle and it may help him get used to having vegetables. Ingredients: ¼ cup unsweetened applesauce ¼ cup frozen blueberries 7 frozen strawberries ½ cup fresh spinach ½ banana ⅛ cup whole milk 1 tablespoon ground flax seed 1 teaspoon cinnamon 1 tablespoon honey Directions: Add all ingredients to the blender except 4 strawberries. Blend for a few minutes, adding strawberries periodically. Continue blending until smooth. (taken from: http://foodiefamilyonthego.com/2013/09/superfood-smoothie-perfect-for-toddlers/)
Does he refuse eating all kinds of veggies or just some? Popular veggie choices for babies are carrots, butternut squash etc. Perhaps you can try pairing the fruits and veggies he likes with some of the veggies he might not like as much. For example, carrots and sweet potato, apple and potatoes, carrots, broccoli and sweet potatoes.