I have no idea how you can explain an invisible God to your son. With that said I want to acknowledge your son for being the kind of person who thinks about things like this and makes up his own mind.
As for things that are invisible that is an interesting subject I hope he will be willing to explore. For instance:
Air – We can’t see it but we know it’s there. We can feel it when the wind blows and when it’s really hot or cold. And if you’re still not sure, try holding your breath for a while. When you finally breathe in, you’ll know it’s not just there but necessary.
Our Spirit or Soul – It is mostly accepted that man is composed of Body, Mind and Spirit. We can see our Bodies and they do things. We can see our Brains and know that thinking and decision making is going on there in our Minds. We can’t see our minds but we are aware of thinking which is also invisible but knowable.
So where are You in there?
You are not just your Body or your Mind. Our thinking can help us determine what is right or wrong, but what part of us Chooses the right or wrong thing to do or say? Some people say our Conscience but we can’t that see that either. Some say our Soul or Spirit. Perhaps they are the same.
I do have a sense there is a part of me, separate from my thinking and that is where I make my choices. It is also the place where I find my passion, my talent, and my spirit.
Words – Also invisible until put into print. They can be used as a powerful asset for good such as for encouragement, teaching, and self-expression or as a wicked weapon for evil such as name calling, bullying, intimidation, and war.
Love – Totally invisible. We can do loving things like cook dinner, play games or help others. We can think loving thoughts and we can express them. But we can’t see love so how do we know it’s there? We can believe we are loved by our families and friends. Sometimes when we Believe strongly enough, we can say we Know we are loved.
But we can’t see Love. We can feel it and we can share it because it is a matter of the heart.
God – Also totally invisible. So how come so many people believe in God? Again, I believe this is a matter of the heart. I, for one, would have difficulty believing that the human body much less the entire universe is an accident. It seems to me that there is some kind of Universal Force or Energy that holds all of it together and moves it forward. Many cultures call this God, Adonai, Allah, Buddha, Karma or many other names. Because I was born into this culture, in America, I call it God.
In many primitive civilizations, people thought the sun ruled the Universe. Others, more advanced, made up their own Gods like Thor, God of war, Adonis and Venus, God and Goddess of love, Neptune, God of the oceans. You can see this list got very long and complicated. Now, many people think of one Universal Force or God.
I hope I didn’t give you an answer as to whether there is a God or not but I hope you thought of a whole lot of questions to think about. Most of all HAVE FUN discovering the invisible.