Less is more.
I almost always urge people to write in the first person. Writing is an act of ego and you might as well admit it.
Write about small, self-contained incidents that are still vivid in your memory. If you remember them, it's because they contain a larger truth that your readers will recognize in their own lives. Think small and you'll wind up finding the big themes in your family saga.
Don’t try to visualize the great mass audience. There is no such audience—every reader is a different person.