Check out this cool website called “Ask a Biologist”!
There are loads of interesting articles to read and a page called “activities” that has puzzles, coloring pages, and games.
How can you use this in your “homeschool”? At our house, I’d explore the site and share things I found interesting over the course of a couple weeks. I’d print some of the coloring pages or word searches and leave them on the coffee or dinner table. If they find it interesting, they’ll look into it more. If they don’t, we’ll move on. I may bring it up again in a few weeks to see if anything strikes their fancy. Even if they don’t have an interest at all, at least they know that sites like this exist and that “biology” is a science!