The problem of most of the parents is that can they really talk to their kids about such a complicated and big subject such as Allah? Can really make the kids understands concepts like, Allah, the day of judgment, prophets, the world, our duty … ? 

The problem of most of the parents is that can they really talk to their kids about such a complicated and big subject such as Allah? Can really make the kids understands concepts like, Allah, the day of judgment, prophets, the world, our duty … ?
Talking about God is important because it can be the best way for kids to make their most important needs and wishes come true, because kids,( even more than parents and bigger ones) need a stable heavenly kingdom that can make their wishes come true. The other good fact about talking about God is that it explains everything in the world, the beauty, feelings, birth or death of a friend, ( by concerning all the natural phenomenon to Allah) and by explaining these a great feeling comes along it because the soul of the kids normally looks for marvels. The kid’s soul looks for marvelous extraordinary things and while it finds a logical answer to all its questions, a pleasant peace comes along it. When the sad and happy memories are linked to God, the relationship between the kid and Allah will gradually get stronger and he will feel some satisfactory in his soul. Talking about God will also give the child security, because in a world that everything ends so quickly, believe in Allah can be the best supporter of the kid’s behavior.

And at last, noticing God and needing Him, will give peace to the soul and the body of the kid, because this feeling is in the heart and it is the nature of the kid. Prophet Muhammad (PBUH) said: until the parents and nearby people don’t move the nature of the kid toward other bad directions every kid believes Allah.
Unfortunately and even though knowing God is really important for kids, but parents are not really aware of how important it is, and they don’t really know how much it can affect the child’s life in a positive way. They spend their children’s energy in going to different classes such as English, arts and so on while they are unaware of the faith and the child’s life finds meaning under the shadow of faith.
They think that working on their religious attractions is not their duty and the children themselves have to grow up and read about these subjects and begin getting faith, and the time is when they are teenagers. But in fact children have the power to understand these things at that time and if the parents don’t talk to them, they will try to find Allah’s signs in their parents’ behavior. And whatever the parents do will stay in their minds much stronger than what they say. And if their deeds are not matching with the religious deeds, the kid won’t understand religion correctly. And this is where we understand the importance of teaching the religion correctly.
If you want your child to understand religion and God well, you have to let him speak out his ideas, and by asking your opinion you can continue the subject. This method is confirmed by many physiologists.
If we know a default about our child’s thoughts at every range of ages it is better and easier for us to help him in the correct direction. In this part we will point to the levels of growing and that what parents should do at every age.
1 to 3 years
We should know that faith in Allah will start from the very beginning years of life, so knowing Allah better in these years can help you very much. In the beginning you can start with the meanings of Allah, Prophets, The Holy Quran, and Imam (a.s). Even though the kid won’t easily understand these things but if you don’t start from those early days, the kid will have problems with bigger definitions when he grows up. And you have to strengthen the bases of faith in love and kindness in them; this is the most important thing that kids would understand God with it. Tell them that Allah loves you and will always support kids. The other point is that the kids need continuous care and support and if the parents give and show them the best of kindness, by trusting them, the children will start to trust and relay on Allah.
3 to 5 years
In this stage it is wrong to ask: what can we do to make our children trust Allah? The correct question is to ask: how do I show him that Allah is present in his life? When children are surprised about the happenings of their surroundings and they fill happy or sad suddenly, you can relate this stuff to Allah and start talking about it. For example if the child is 5 and he is sad about a grand pa’s death, and asks you what will happen to grand pa now? Will he go to heaven? At this level he needs confirmation. You have to ask him about his idea, and then accept his thoughts. Because he’s probably going to say, grand pa is with angels. And even when your kid is excited and happy about a new child getting born, you can talk about God’s important role in creating the baby. Or even when you are eating you can tell the child that these foods are from Allah and we should thank Him for all His blessings, and then along with your kid say thanks to Allah. 6:01
At the age of 3-5 kids normally think that Allah is a sacred and religious person. So they normally ask: where does God sleep? What does He eat? Where does He live? For answering these types of questions, you have to be careful. First to cool down the curiosity and be honest, you’d better say I don’t know, and you have to remember that the kid is not big enough to understand that Allah doesn’t sleep or eat anything. If you say this as an answer he/she might even get more confused.
Then you can ask the child more questions to keep her attracted to the subject. You also have to remember that you should never make fun of the questions your kid asks, always be serious, and know that your child is not in the age of reviewing your words. So while you’re talking to a kg1 kid, know that you are the expert of the subject, so be careful and don’t say things that might make you disappointed afterwards. For example don’t tell them Allah will punish you if you behave badly. Then she will always image Allah as an angry father that is waiting to punish her the minute she did something wrong.
6-10 years
The children that it’s their first year of school, normally ask logical questions about Allah such as: is God the reason of death? Does Allah understand whatever we do? The important thing is that parent apart from answering their questions, should help the kids believe in Allah. Sometimes the kids might even ask about the reason of natural things such as earthquakes, thunders, illnesses… you have to be careful and not relate them straightly to Allah. Sometimes they might ask; why is this person blind? Or why did the other person die? You better answer them with scientific reasons and relate it to nature.
The other way of creating a relationship with Allah is to read them Islamic children stories. They can use these stories in their normal life; choose the books in a way that shows them Allah is always with them.
Pre-teenage years
The young teens have unusual changes in their body and soul, this makes them want to be freer, and by knowing Allah it helps them to understand that he is the source of the worlds order. They also want to know the relationship between God and all the bad and disastrous things that happen in life. So we have to tell them that Allah doesn’t send us disasters, He indeed He gives us strength to solve them out. Allah has given us the gift of helping others too.
Teenager
At these years teenagers ask a lot and sometimes complain about the religious facts, your duty is to follow them and NOT talk to them about religious words. You just have to try and tell them about God related to their own problems. And you should know that complaining and doubting is the beginning of faith. When the teen feels useless and unsafe, you have to assure them that Allah loves all of us. When the teens are affected by their classmates breaking rules and doing illegal things such as using drugs and __having a relationship with the other sex you have to tell them that Allah is the only person that is looking at what we do, and he will surely punish us if we do wrong and he will also give us reward for the good deeds.
Conclusion:
So teaching monotheism to the kids is like teaching them how to bike, first you row it and show them and then you handle it to the kid itself it’s up to them if they want to ride or not, but remember if you start for the early years you have done a big step and it might stay until the end of the life of the kid.

Source: 3rdimam