What you need:
Scriptures (Genesis 11 and Ether 1:33)
Tower of Babel coloring page
Sheet cake cut into approximately 3x3 pieces (any cake recipe or a box mix will work)
Frosting (again make your own or buy a tub)
We showed our kids the coloring page and gave them a brief intro to what the Tower of Babel was. They colored the picture while we told them more of the story, including about the Brother of Jared and a discussion about how we get to Heaven.
After that we had some real fun making our own Tower of Babel out of cake and frosting.
I handed everyone a piece of the cut up cake (bricks) and we all took turns adding frosting (morter) and stacking them together.
This was a lot of fun and of course the kids loved eating the tower after it collapsed.