The Garvies Point Museum in Glen Cove has an interesting mix of geological and historical exhibits that will engage kids who are interested in dinosaurs, rocks or Native Americans.
The South Shore Nature Center in East Islip is the home of a small museum where kids can get a closeup look at some native Long Island wildlife, as well as an extensive complex of walking trails.
The Tanglewood Nature Preserve in Rockville Centre is the home of the Center for Science Teaching and Learning, featuring many live animal displays and a nature walk around the pond.
The Long Island Museum in Stony Brook is an eclectic collection of vintage horse-drawn carriages, decoys, artwork and special exhibits on a park-like setting off of Route 25A.