How does free will explains children with cancer or is that good thing?
I think free will can be attributed only to actions people are doing. But not everything can be attributed to people (or other animals).
Even without the theology, a person suffering due to a forebear's poor decision is well-understood: a decent percentage if people think it's the natural order for a child to go hungry if their parents are drug-addicts or imprisoned.
If someone gets cancer as toddler who's fault is that? If someone is born with disability, with caused by new mutation, who's fault is that? Are these part of free will? Do you thing that it is good that it is happening?