While looking for information about the Battle of Long Island, I stumbled across two good maps that you could use for a Brandywine wargame scenario. Both show the terrain as close as possible to what it was like in 1777.
The first one (see below) can be found at: http://www.campaign1776.org/battlefields/brandywine/maps/battle-of-brandywine.html. Go to this link from the same page: http://www.campaign1776.org/revolutionary-war/, then click on select a battlefield for more maps. Some are very good (like the Camden and King’s Mountain maps). The Guilford Courthouse map suffers from some order of battle errors and lacks the fields that the American militia lined up along.
The second one (see below) can be found at: http://www.landscapes2.org/publications/historic/battlebrandywine.cfm. This site also has a variety of other useful maps about the Battle of Brandywine.