Jump indoor party center in Ronkonkoma is a large play space that is filled with inflatable bounce houses and a video game center. It's primary business is parties, but they have a daily open play time as well.
Corey Creek Park is a Brookhaven Town park located right on the Great South Bay in Blue Point. Its unique playground, located right on the beach, is a good visit even when the swimming weather has gone.
Tucked alongside the intersection of Sunrise Highway and the Robert Moses Causeway in West Islip, Anthony Casamento Park is the the home of a number of athletic fields, a swimming pool and a small playground.
Adventureland, on Route 110 in Farmingdale, is the last of Long Island's large amusement parks. With rides for small kids and large, indoor and outdoor spaces and well-manicured grounds, there are good reasons why it has survived.