Hello from Germany (we hate Nazis, too),
I've just asked my mother (retired primary school teacher, primary school is for ages 6-10 here); she does not recall teaching her school kids about the Holocaust, definitely not before 4th grade (age 9-10) and definitely not in detail.
She mentioned my brother was shown "Schindler's List" in 6th grade and she found that quite egregious.
You have to know that we are taught A LOT about the Holocaust in schools in Germany. It's almost too much, because you become a little jaded.
In my opinion your kid is way too young to be confronted with such horrors. Same about 9/11, probably too early.
I very much appreciate you being that thoughtful about teaching your kids politically and historically.
The best you can do for your kids is make them think critically, question the authorities, question themselves, be free thinkers.