Swamp White Oak, and Pin Oaks will do well there. PawPaw need high humus soils.River Birch will do well in the same area as those Siberian Elms.
The riparian buffer plants will all depend on the amount and level of the water. Arrowhead and Pickerelweed do not like highly varying water levels - they do better with 0 to 24" bouncing levels. Horsetail Rush or Scouring Rush grows where the water levels bounce and they don't need good soil. They are hard to get rid of though.
Most types of rush will do OK, but that all depends on the amount of water and level of the water.
Black Walnuts don't do well with flooding.......
Check the pH of the sandy soil, you might have to add lime on an annual basis.
