The thing is, my kids don't even know what "Injuns" are! In Peter Pan they look like very red people wearing feathers and dancing around fires. They are no more real to them than the mermaids in Mermaid Lagoon or the pirates on Hook's ship! They don't understand that "Injun" is a reference to Indian, which is being used to describe Native Americans rather than people from India. They don't realize that there are still pirates in the world today, but they look nothing like the pirates in Peter Pan or Pirates of the Caribbean. All of that is above their heads. One day when they are older and know more about the world I expect we will talk about it, but right now Peter Pan and the like fall squarely into fantasy, and bear no relation to anything real in the world.
The kids need to learn that every work of fiction is the imagination and interpretation of its authors, and is not always based on reality. As they grow older they will learn what is "real" from reading, watching real life shows on TV (National Geograhpic, Discovery etc., which my kids already love) and school. They will realize for themselves that Native Americans are nothing like they are portrayed on Peter Pan.