You can use Homeschool Planet, a popular online homeschool planner, from a browser on your computer or mobile device. While there is not a separate app for phones and tablets, there is a mobile version that works well. Homeschool Planet is already pre-coordinated with many curricula, making it especially easy to add lessons to your homeschool calendar. Your kids can have their own log-ins to Homeschool Planet, and you can also print your plans if you want them to follow along on paper. There's a Homeschool Planet YouTube channel with tutorials and user guides. See Homeschool Planet's Frequently Asked Questions for more information on how to use the program.