(Note that unless the child asks a question, or is likely to be exposed to a question soon, you don’t have to attract his attention to something that hasn’t come to his mind. You only need to teach him the basic belief, like in the rhyme recently posted. Moreover, when addressing a child you don’t have to be complete all the time, but cover the issues that suit his mind and circumstances. In other words, you don’t have to cover all potential objections of deviants. I have put some extra things in footnotes that some children might need. That being said, the following is the answer:)
We have to look at what they believe and group them, then we can decide what is wrong with these groups.
First let us look at what they believe about God.
If we take all the people in the world, they will either believe that God exists or not.
Some believe that God does not exist. Those people are called atheists. They are the silliest people, because this world needs someone to give it the color and shape it has.
If you showed a drawing to him of a donkey, an atheist would say that someone drew that donkey. He would be sure that someone drew the shape of that donkey, and put color on it. He would laugh at you if you told him that no one drew it, or that the pen and paper got together by themselves and made the drawing. But if the color and shape of a simple drawing cannot happen without someone drawing it, how can they then believe that all the different things around us, with colors and shapes just like the donkey, gave themselves the color and shape they have? This is even more crazy than saying that a drawing was not drawn by anyone, because many of the things around us are much more amazing than a simple drawing. A baby in the mother’s stomach, for example, starts as a simple drop of liquid. Then that liquid becomes a peace of blood, then a piece of meat, and then it starts to get the shape of a human, with skin on the meat, arms, legs, stomach, intestine, blood vessels, a heart that beats to pump blood to all the parts of the body, blood that has in it all the ingredients in its mix that the different parts need, and more. Now if a simple donkey drawing must have a drawer to give it simple shape and color, how can they claim that this human does not need a creator to give it all of these things. This is really silly.
So the Creator definitely exists.
Now we are left with the group of people that believe that the Creator exists. We now need to group these to see who is right and who is wrong.
Those people who believe there is a creator, either say that there is only one creator, or that there are more.
There cannot be more than one, because if there were two that wanted to create a human, then they would need to agree on the shape. If they could not agree then this means that the one that did not get what he wanted is weak. This means that he is not god, because god cannot be weak. If they always agreed, then this means that both would be weak, because they would need to agree, and needing is weakness.
So the Creator is definitely One, and not more.
Now we are left with the group of people that say that the Creator exists, and is only One. We now need to group these to see who is right and who is wrong. Those are the Muslims, Christans, Jews, and some liars that claim to be Muslims called wahabis.
Those people who say there is only One Creator, either say that He is something with a shape or not.
Those who say He has a shape are very silly. I think you can understand why. Just remember what we said about the donkey drawing. We said that the donkey needs a drawer to draw its shape. So anything with a shape needs someone to give it shape. When they say that God has a shape, they are saying that He needs a creator. This means that He would be a creation, and not the Creator.
Christians and Jews believe that the creator has a shape, because it says in their book: “God created man in his own image, in the image of God he created man; male and female he created them.” As you know, image means shape. Another word they use for shape is limit, which is the word wahabis use – don’t let them fool you. What they are saying then, even if they do not admit it, is that God needs a creator. By saying no to this, they become just like the atheist with the donkey drawing. They will be saying that some simple shape must have someone give it its shape, but that the human shape does not. This is because they believe that god has a human shape, but was not given it.
So the Creator definitely does not have a shape.
Muslims do not believe that Aļļaah has a shape, so He does not need a creator. As you can see, Muslims have the only logical belief about Aļļaah.
You should also understand that the human that draws donkeys is not creating the drawing. This is because the human is weak. He was created by Aļļaah, and after being created, all the movements of his body is a different shape. Even when his little finger moves, this is a different shape from before moving it. He could not have moved it if Aļļaah did not create that new shape. This means that the drawing he did was created by Aļļaah, because Aļļaah created the drawer’s movements. This means it was Aļļaah that created the drawing, and that the drawer was only moving by movements created by Aļļaah. Yes, it is true that you can usually move your finger when you want, but that does not mean you created the movement. If you think about it, you do not know how you made your finger move. You do not know what muscle is working, or how you get your muscles to work. There are many things that happen in the body when you move your finger you do not control, such as millions of little parts of each muscle contracting, electricity coming from your brain to make them move, and many other things. This tells you clearly that it is Aļļaah that controls those things, and not you, so it is Aļļaah that creates your movement, and not you.
 For kids that have been exposed to atheist arguments, or you fear will be soon, you might add something like this: Sometimes they will say, “but we saw that the donkey has a drawer, and we did not see any creator of humans.” This is a lie, because they did not see the drawer of all donkey drawings. This means they believe that the shape and color of the drawing must have a drawer, even if they did not see him. This means that they should admit that more amazing things, like a human being, must have a creator also.
 This paragraph is for kids that need this clarification. It is an important one, if they are ready to understand. Word of note: don’t underestimate your children’s intelligence. I have personally taught children at 3-4 years of age that Aļļaah exists without being in a place.
For kids with even more mature mind’s, you can further add to the last paragraph: You can understand this, because you know that all shapes need a creator. When a muscle contracts, it means it becomes shorter, so it is a different shape. Even electricity from the brain is like that, because it flows in a path from the brain to the muscle, and a path is a shape. All of these shapes are created by Aļļaah, so it is Aļļaah that creates your movements.