What about those families who teach their kids that evolution doesn't exist?

I say, let them.

The homeschooling parents who are teaching their kids this information were probably educated in a traditional public or private school.  Attending a traditional school did not keep these parents from developing their extreme views.  There are all types of extreme views and kids are going to hear them from their parents, whether they are homeschooled or not.  Finally, with all the media out there, it is harder and harder for people to isolate themselves (or their kids) from mainstream ideas---whether they are good or bad.  So, I say let parents teach what they want to teach, within the confines of the state homeschooling regulations.  Their kids will eventually develop their own views--perhaps to their parents' chagrin.