The island trees may not survive the saturation if the pond holds to full level. I hope they do but don't be suprised if they don't. If the worst happens you can always plant bald cypress on the island or a weeping willow. Check out my willow
http://www.rockytoppers.com/the_pond.htm it is the first picture on the right under pond construction. This tree was planted 4.5 years ago. it was a seedling from home depot about the size of your little finger. A beaver eat it off at ground level at 2 years old. IT was a 6 inch dia at that time. it grew back like a bush out of the stump. I trimmed all but 3 branches. It is not a tree with three forks. Weeping willows are fast growers but do not live long. I've planted live oaks next to them .hopefully by the time they die the oaks will be nice size 20 years or so. The bald cypress has also grown very fast and will last a lot longer than a willow. The picture on the left center of peir was a 3inch 3 years ago. it's now a 10 inch dia.
good luck it is very nice.
