How about Weeping Willows for your island? They are great trees for keeping a check on soil erosion and tamping muddy puddles. The graceful canopy of these shade trees also makes for an exotic looking privacy screen. Check out this picture and you�ll know what I�m talking about! A couple of Weeping Willow trees will look absolutely stunning on your island.
Link: http://www.fast-growing-trees.com/WeepingWillow.htm
Another flowering tree that you can plant for show on your island is the Okame Cherry Tree which is usually one of the first trees to blossom during spring