Picked Mackinaw - I've never been but I've heard so many good things about the island. Virginia Beach would be my second choice. I live too close to enjoy Niagara Falls anymore...been there, bought the tshirt.
I've actually been everywhere on your list except Arkansas. That is a first for me since I am not very well traveled. Mackinaw is fantastic. I have been there with young children, old, grumpy relatives, teens and everyone in between and nobody has ever been disappointed........well, except the one time my front crown fell off and the only dentist on the island had a family emergency so I walked around toothless for two days.
I picked Mackinaw Island but not out of experience. I've just heard it is wonderful and would love to go myself some day. I'd love to see Niagra Falls, too.