You may choose to coordinate your science work stations with topics that you know certain grade levels are studying. Keep your eye on the pacing guide to see if you can help to reinforce concepts being taught in the classroom. For example, at our school, first grade and fourth grade study soil at the same time. That's when I set up soil centers in the library.
Try one of these. I think that the student and teacher enthusiasm will motivate you to add more and more of these to your work station rotation!
Especially in October, a live spider in the library is a delight to observe! You can pair it with your spider books and create activities to go along with them.
When our students are studying soil, I like to bring worms into the library. I'm still working on the best way to observe them, while they're trying to hide in the dirt. But our students love to try to spot the little wigglers.
In the spring when we are learning about life cycles, we bring a tank of tadpoles into the library. They are fun to watch and easy to feed!