Land use advice
If you are located in New Castle County I would recommend first calling the New Castle County Extension Office at (302) 831-2667. They will put you in touch with someone who can talk to you about land use. Phone numbers for the other Delaware Extension offices are 302-730-4000 for Kent Co. and 856-7303 for Sussex Co.
If you haven't done so already, I also recommend that you begin doing some reading about the two crops you are interested in growing. The Mid-Atlantic Berry Guide is a good place to start for blueberries. For grapes you could start with Penn State's Wine Grape Production Guide.