If there is a God, I don't think he/she/it is responsible for every little/big thing that happens to us. Creating a beginning for a large ecosystem (the universe) that takes care of itself would be far more logical.
I like to see God as a person that makes a snowball, the snowball meaning the main building blocks for everything (like atoms and the energy of which they consist, ect.). He made the ball, but he/she/it does not decide how it rolls down the hill. Heck, that God might not even know that the human race or this planet exists. (Not trying to bash anyone's religion of course. These are merely personal theories, I do not see them as the ultimate truth. ;3)
Blaming things like cancer on God is just too easy. Children get cancer because they're human, like us. And this might sound blunt, but I have no more sympathy for a child having cancer, then I have for any other person having cancer. It equally sad.
Kids get cancer because humans do. It's sad, but it's just as simple as that. :C