My family had a great trip to 1000 Islands(NY), in the Memorial Day long weekend.  According to Wiki, 1000 Islands area is very popular among vacationers, campers, and boaters, and is often referred to as the "fresh water boating capital of the world".

We stayed few nights in a Hotel, at the banks of Lake Ontario and saw the great sun set view. You can have so much fun if you plan well in advance for all other attractions near Alexandria bay, NY.

Two things that you must Do when you are at 1000 Islands.

1) Boat tour by Uncle Sam,

2) Get down and visit Boldt Castle Island and stay at Hotel where you can see the beautiful 1000 islands view from your room.

and optional visits if you had time are
Thousand Island bridge between NY and Canada, Kart race track, Aquarium Zoo and etc..

The First attraction in 1000 Islands is the Boat tour. This Boat tour covers maximum islands with in two and half hour, where you can see the smallest to largest Island. A guide will explain you the history behind the Castles and houses build on those Islands by famous celebrities.

The second attraction in 1000 Islands is to get down and visit Boldt Castle. You can feel the beauty of Boldt islands with grate buildings and you can also see some parts of under construction Castle.

Know more details about on 1000 Islands

1000 Islands Wiki

Uncle Sam boat Tour

Chamber of commerce website