The Sweetbriar Nature Center in Smithtown is home to a large rehabilitation aviary, public gardens, a natural history museum, working farm and a vivarium.
The Suffolk County park at Lake Ronkonkoma is the home of a very large playground complex as well as athletic fields, mobile pier and a non-swimming beach.
The Holtsville Ecology Center in (where else?) Holtsville showcases a number of animals that have been rescued from the wild as well as your standard farm animals. The site also features a playground, nature walk and Brookhaven Town pool.
The Long Island Game Farm in Manorville is one of LI's oldest family attractions featuring animals, shows, rides, and lots of hands-on learning opportunities.
Belmont Lake State Park in North Babylon features acres of hiking trails, boat rentals, some of Long Island's best fishing, and a waterfront playground.
Set in a quiet space off of route 25A just west of Cold Spring Harbor village, the fish hatchery gives kids an opportunity to see many of Long Island's native fish species up close.
The Cradle of Aviation Museum in Garden City is a great place for kids to explore the history of flight and air travel with a special eye towards Long Island's contributions to aerospace. With a combination of historic displays and hands-on activities, there's plenty to do for children of all ages.