As mentioned above, you can use posterboard, but I simply used two plain file folders to make our lap book. I glued the two file folders together so that I had a folder that opened from both the right and the left. Then I covered the sides with some cardstock to give the book a little more color, because kids love color. Of course, you can always just buy colored file folders, too, but those cost a little bit more.
On the cover of the lap book, I simply put a photo of the ancestor we were profiling, his name, and the years of his birth and death. On the next page, after you lift the cover, I made a list of people showing HOW this man fits into the child's genealogy. I think this is a really important visual feature, especially for ancestors who lived so far removed from your child's time. This man is my kids' 4th great-grandfather, which in and of itself is hard to comprehend, but if I trace him back starting with their dad, grandpa and great-grandma (all of whom they know personally), then it doesn't seem as abstract.
©2016 Emily Kowalski Schroeder