I also found this great image from The University of New Mexico, that I was able to laminate and put up on our bulletin board to study. It identifies the many parts of seeds and germinating plants. You will find a lot of other helpful and very detailed reading on their site.
After the sunflowers sprout, we will plant them in the yard and then continue to observe them to see how long it takes for the flowers to bloom and return to seed once again. The other seedlings we will scatter under the bird feeder for the rabbits to munch on.
This is an easy and complete life cycle to learn from, plus you might even get some fresh sunflowers seeds to eat yourself when you are finished!