I love children for their sense of wonder! Babies can teach their grandfathers anew how to be enchanted with life. That is the great gift my grandchildren gave me. Revisiting wonder, enchantment, joy. They also made me ashamed that I lost those child-like qualities somewhere along the path between early childhood and adulthood.
But living and remembering are two dramatically different things. For an old man to re-capture a sense of wonder is not an exercise of the intellect rather an exercise of the heart propelled by a love for another so intense it aches.
Joy is different from happiness — although they have many of the same attributes. Happiness is a response to something we gained or attained. Joy simply is. Joy is closer to God than happiness. C.S. Lewis said that Joy is the serious business of heaven.
A toddler tries to taste a flower; in her mind pretty must also be tasty. We laugh to watch her discover that what is pleasing to the eye is not always pleasing to the tongue. Yet in her world it should be. Perhaps in the next world the two will merge.
The beauty of the world is only a pale shadow, and a small inkling of heaven’s beauty too profound and perfect for us to accept in our present bodies and form. We must yet be transformed. 
Simple joys are best. They cannot be harnessed and sold to the highest bidder, to the exclusion of those who can’t pay. Joy is a spiritual state not a commodity. Joy is the possession of babies and small children that they freely offer to those who are near and open to the idea of humbling themselves, becoming child-like, in order to receive their divine gift of joy.
I believe a man is never so tall as when he welcomes a child and stoops to enter their world.
 1John 3.2 (cf. 1Corinthians 15.50-53, 2Corinthians 5.3-4, Philippians 3.21.)