The title suggests the topic for this blog. Where is God when people suffer, especially children?
This is a tough one. After Adam and Eve made the choice they did Genesis 3 tells us that there were consequences for the world. Women having pain in child birth and eyes for her husband...and the ground would produce thorns. Until then paradise was thorn less. The new reality, since paradise was lost, is that this world is no longer a paradise. Thorns, hardships, struggles, pain, difficulty all exist and come to us indiscriminately. If you read 2 Corinthians 11:22-33 there is a long list of some of Paul's difficulties. Some of his hardships were the result of other people (lashes), some were the result of nature (wind storm/ship wreck), one was within himself (inwardly burning) and some were some false brothers. Troubles may come due to paradise being lost, like a storm which causes a shipwreck. People cause suffering -their decisions which effect others. The truth is this thorny world may bring any kind of suffering for anyone, adult or child, and it is just part of living in a "groaning" (see Romans 8) world.
As you continue with 2 Cor. 12:7-10 you learn that what God wants from us is faith. Trusting him is not about how well we or our children are or how well we escape difficulty. We trust God not matter what and it is our weakness that turns us to him. It is always hard to see suffering. We need to let suffering remind us of our need for God. Easier said then done, I know and you may need to read this back to me some day when I suffer and do not know why or watch a loved one suffer.