Kim Edward's novel The Memory Keeper's Daughter tells the story of two families--one which keeps a secret and one which lives in relative secret. David and Norah have twins; David (a doctor and the one who delivered his children) makes a life-changing decision to tell his wife the second baby died. In fact, the baby girl was born with Downs Syndrome, and he asked his nurse, Caroline, to take her to an institution--which she ultimately could not do. Both small families go on to live their lives. David, Norah, and their son Paul all suffer the consequences of this decision, though only David knows the secret which is the root of their deteriorating relationships. Caroline raises Phoebe with a wonderful man, Al, and they do nothing but grow closer together as they face the external battle of an equal education for their daughter.
As for the lessons, consider the following broad ideas which can be explored in the context of this novel:
Doing the wrong thing, even for the right reason, is bound to have consequences.
A family which does not communicate is likely to have little to hold it together when times get difficult.
One must be willing to fight for something about which one feels passionate.
Having money does not guarantee happiness; not having money does not preclude happiness.
A disability is only as significant as people make it; having a disability does not relegate one to second-class status.
This should get you started, anyway. Best of luck!