@edgarblythe,
This worldly life is a test and is temporary. We see this on daily basis. How many people die every day. Does anything live forever in this world? No
Do we get absolute happiness in this world? No
The fact that these pains and pleasures coexist is one of the signs of the Hereafter, for divine wisdom has decreed that there should be two abodes: an abode that is devoted fully to pleasure, in which there is no pain at all, and an abode that is devoted fully to pain in which there is no pleasure at all. The former abode is Paradise and the latter abode is Hell.
Going back to your question, who created children? God did. Can He take them back? Absolutely He can. Everyone of us is created by God and some lives in this world for few seconds and some for many years. Each one of us has a different test and some of us are created only as a reminder for others.
Why the kids suffer? To remind us that this world is not a place of absolute peace and happiness. To remind us that everything in this world is temporary and will die or end. These sufferings and tragedies are reminders for people to get back on straight path. The children who are killed or die are in heavens and will remain their happy forever. If someone can find an eternal happiness at the cost of suffering in this world which is temporary then its not a bad deal at all. Compare life of 100 years with infinity will that mean anything?
Everyone who comes in this world, comes with empty hand and when dies leaves the world with empty hands. Only thing which is left is our actions which are saved and will be given to us when we are resurrected. Just like rain water can give life to dead land, similary we will be given life after death when the hour comes.
Some people believe that our life ends when we die and we all become dust. We now know that DNA lives many years after our death and we can track back many things from DNA. This was not know a century ago. If human being with their limited knowledge can track back thing from DNA, do you think our creator can't retrieve all the information from our DNA? Something to think about ....
Why every human being has unique finger prints? Is this just accidental? Something to seriously think about....