When teaching about the tower of Babel a really cool idea is to have the kids build an actual tower!
Begin with reading the story, telling how the people built a huge tower. Read Genesis 11:1-4. Once you reach this point stop and have your kids begin to build a tower. Let them try to make it as tall as they possibly can, as if they were trying to build it to reach Heaven. Then once they complete it have them all sit back down and read Genesis 11:5-9. Even though God did not smash down the tower have the kids destroy their tower to symbolize how the people stopped building it and never finished it.
This could be a great activity to do at home together or it could be great for a sunday school class. The best part about it is that it allows kids to interact with the Bible story with their own two hands. This is a great way of learning because when you interact with something you will remember it longer.