Have you looked up the 17 VanIderstine surnames in the PEI phone listings - http://www.canada411.comhttp://www.canada411.com -
With one exception (the last one in Wilmot) they all live in the eastern end of the island, up to the capital city area of Charlottetown. Main locations are Montague, Murray River, Murray Harbour, and Vernon Bridge.
You might want to contact some of them to see what they know. Someone in the family must be an historian. PEI Time is ONE HOUR LATER than U.S. Eastern or Ontario Time.