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.
Just west of the Wantagh Parkway, Wantagh Park offers many recreation areas on a waterfront location including playing fields and tennis courts, pool and a large playground.
Lido Beach is the town of Hempstead's huge waterfront complex in Long Beach. There is an ocean beach, tennis, shuffleboard, softball fields, pools and a great playground.
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.