One way you could impress upon young children the goodness of God is by showing them the beauty as found in nature, including the colors, textures and shapes. This can be done with pictures; going for walks in the woods, creek; having a pet they must care for, allowing it to reproduce, having babies.
When I was a child I loved to trail dad all over the farm, helping with the feeding of all the animals, chickens and turkeys. Many times it was dark by the time we finished. As I walked with dad, my hand in his large ones, we would peer up into the sky, stars shining ever so brightly and we would talk about God, how awesome He is to have made the stars and hung them up there in such a grand way. Watching lambs play, or watching sows birth their young - even assisting in this process filled me with awe at an Almighty creator who made things so beautiful, so awesome.
I still recall vividly the sense of awe I felt for God at these moments. It has never left me.