This would make a great family or homeschool project. You would first need to do some online research about the elements you would like added to the cookbook. Some suggestions are:
table of contents
this for that information
information on the different types of pumpkin
information on making homemade pumpkin puree, by baking or boiling
information on freezing pumpkin, or the finished recipes
how to store roasted pumpkin seeds
You may also want to add a photograph of finished recipes, or of your children making each recipe. A nice two-page spread would be the recipe and picture on one page, and a journaled story about making or eating the dish on the next page.
You may also want to make this book in the shape of a pumpkin for something fun to do.
You will want to use only your favorite holiday/harvest pumpkin recipes, so you will have to try them all out first. This can be a lot of fun. You will also want to make sure that you now how to prepare relevant recipes for the freezer.
Here are some pumpkin recipe ideas:
pumpkin cake with cream cheese frosting
soups, and soups served in hollowed out pumpkins
roasted pumpkin seeds