We've spent the last year reading through our Herb Fairies books and the kids still love them! It's been such a cool way for them to learn about different herbs and really internalize their medicinal uses. Sam was even able to use an herb once when we were out hiking. It was such a proud moment for him.
I also took the kids to an herbal class that a friend put together. It was SO fun for them to pick, taste, smell, eat and create with herbs! That really is the best way to learn about them. They made medicinal honey, tummy tablets, and teas. The class, the Herb Fairies books, our own gardening and hiking, really worked together to start a foundation of basic herbal knowledge. I feel like that sort of knowledge is so empowering. We also love the game Wildcraft, by the same company.
The Herb Fairies website has lots of great content with recipes, coloring pages and activities. I think they're starting up their 2014 book club soon (you read the books throughout the year, learning about the herbs that are in season). I feel like this was such a great supplement to our homeschooling and something we can revisit each year, going more in depth as they get older.