Here is a pretty cool youtube history channel. They look at the progression of World War Two a week at a time as it happened 75 years ago. It might be pretty fun to watch with your kids.
https://www.youtube.com/channel/UCP1AejCL4DA7jYkZAELRhHQ
https://www.youtube.com/channel/UCP1AejCL4DA7jYkZAELRhHQ