Bananas are good for kids as it is loaded with fiber, vitamins and minerals. The same goes with pears. Pears have good amount of dietary fiber, vitamin C, and potassium. But as coconuts have high amount of fat they may not be good for kids. Probably you can go for tender coconuts and coconut water. Coconut water is the nature's best refreshing drink and are composed of sugars, vitamins, electrolytes, amino acids, and cytokine. Even though you can use cucumber in a pear-banana shake, it is commonly used by adults for detoxification. So, I doubt whether you should bother adding cucumber to your shake. Cucumber is normally added with spinach to prepare green shake, which has the property to detoxify body. You can make delicious pear-banana shake using tender coconut water. First chop the pears and bananas into small sized cubes, add 4- 5 scoops of vanilla ice cream, 1 cup of low fat milk, 1 cup of tender coconut water, and 1/2 tsp of vanilla extract and 1 tsp of agave nector. Blend this well for a delicious shake.
You can keep your main ingredients for the shake as pear, banana and coconut water, and make variations to it. For instance, you can add oranges to the above recipe, as adding oranges would add a tangy flavor to the shake. You can also try adding, 3/4 cup of berry juice or 1 cup of blueberries or 1 packet of vanilla stevia, or 1 cup of pomegranate. For rich and creamy shake, you can add 1 cup of mixed nuts like pecan, cashew, almonds, figs, and dates.