No, it's not on 416, but on 401. Go down south on 416 to the end, then take 401 west in the direction of Toronto for about 1.5 hrs, you'll see the Thousand Islands Parkway exit to your left, and a strip of mall on your right hand side. Go on the parkway till the end and just follow the sign, you won't miss it.
I'd suggest taking the 3-hr tour boat, but it'll dock on the usa side, so make sure you have US visa or Canadian document (passport, citizenship card, etc...).
