I grow sunflowers in my yard for beauty, beneficial insects, and wildlife. The bonus is that I can harvest the sunflower heads for myself and roast the seeds. This is another project that your kids can participate in easily. In fact, it's a great project for kids groups and clubs like 4H, girl and boy scouts, or after school programs. While all sunflowers are beautiful and attract wildlife, usually the best sunflower heads to use are those produced by the bigger sunflowers like Giant Gray Stripe, Sunzilla, and Mammoth.
After you cut the flower heads off the stalk, let the heads dry until the front of the heads turn a crispy brown and the back of the heads are yellowish. At this point, you can lay them flat on a covered table and let the kids rub the front of the sunflower heads. The seeds will easily pop out and young kids will be quite entertained.
After they seeds are all out of the flower heads, carefully go through the seed pile and pick out undesirable pieces of stem, etc. For salted seeds in the shell, you'll need a bowl or other container with a couple of quarts of water. Add about 1/3 - 1/2 cup of table salt to the water, add the sunflower seeds, and let them soak in the salt water overnight. Another way to get the salt onto the shells is to put the salt water and seeds in a pot and let it simmer for 2 hours on the stove. If you'd rather have unsalted seeds, skip this whole section and go straight to roasting.
The next day, drain the salt water from the seeds and lightly dry them with a paper towel. Preheat the oven to 300 degrees. *Spread your seeds on a large cookie sheet and let them roast for 30-40 minutes in the oven. You can stir them around after 20 minutes or so, if you'd like. You'll want to watch for the seeds to become a little brown and looking crisp - or you can pull them out when they just look dry.
Sometimes, you'll see a little crack on the shells as they roast. The finished product is an individual thing and you may want to experiment with a few batches until you get them to cook they way you enjoy eating them. At this point, pull them out of the oven and let them cool. You can add a little more salt at this time or some people add some melted butter over the top of the seeds after they come out of the oven. I've not tried the butter idea, but I'm usually up for anything with added butter - so it sounds right to me. To keep sunflower seeds, once cooled, store them in a tightly sealed jar or container.
*Only adults should be handling the seeds around the oven.