I would actually hesitate to say that Saint-Exupery's point is to portray a child's life as "easier," meaning lacking in difficulty or effort and free of worry and care (Collins English Dictionary). On the contrary, both the little prince and even the narrator were described as having very difficult times in their childhood. Instead, Saint-Exupery argues that the child and the child's vision of the world is far more pure and even far more practical because children's visions have not yet been influenced by materialism in the way that all of the adults have been influenced by materialism. However, there is one chapter in the book that can be interpreted as portraying children as having easier lives while also portraying children as far more practical than adults. In Chapter 22, the railroad switchman has some very enlightening things to say about children.
In fact, the railroad switchman has some very interesting things to say about adults as well as children. When the little prince sees for the first time the trains full of travelers thundering past, he notes that they seem to be in a "great hurry" and asks the switchman the very insightful question, "What are they looking for?" The switchman gives the equally enlightening reply, "Not even the locomotive engineer knows that" (Ch. 22). In other words, Saint-Exupery is using this exchange to point out the social reality that humanity is always in a rush to get they don't know where and to do they don't know what. Humanity lacks clear foresight. The lack of foresight is further revealed in this exchange when the switchman further points out that "no one is ever satisfied where he is"; and yet, despite their lack of satisfaction and their eagerness to get who knows where, they are actually all traveling blind. As the switchman points out, "They are all asleep ... or if they are not asleep they are yawning." The image of sleep is again a reference to blindness or lack of foresight. The switchman further points out that only the children are awake in the train cars and "flattening their noses against the windowpanes" in pure excitement and curiosity. In other words, only children are awake enough and have enough foresight to still enjoy the world. The prince sheds further enlightenment when he points out that "only the children know what they are looking for." In other words, only children are still pure enough at heart to still be able to see what's truly valuable in this world and to pursue it; only children are non-materialistic or spiritual enough to truly know what is worth wanting. The prince continues with an analogy of a child crying when a rag doll is taken away, but not to show that the child is materialistic. Instead, like the fox, the prince is pointing out that the time spent on something or someone makes that something/someone valuable and that time spent equates to love. Therefore, only children are capable of understanding the things that are truly important, such as love. Since children understand what they want, what is truly important, and don't struggle in vain searching for it like adults, we can say that children have an easier time of life than adults.
Therefore, if you are going to write an essay about how life is easier for children, I would focus on analyzing this chapter and show how the easiness of life for children is related to their ability to still know what's truly important in this world.