You probably already have these but in case you don't, you might like to look at the following:
Major & Mrs Holt's Battlefield Guide: Normandy Landing Beaches
IGN map D Day 6.6.44 (available here: http://www.mapsworldwide.com/map_28799.htm
The first is one of a series of guidebooks detailing itineraries for exploring the sites of various important battles (other titles are: Somme, Ypres and Gallipoli). It is very biased towards travel on land but does contain some information that may be of interest and many useful maps and interesting photos. It also has an accompanying map and may be purchased from Amazon.
The second is a map of the Northern French coast highlighting various sites of interest. Again, it is mainly land based but only costs £5.99 so worth a look if you have an interest in military history.
Another thought (if you're really serious about researching your trip) would be to make a visit to Normandy to the various war museums and monuments, most (if not all) of which are listed in Major & Mrs Holt's Battlefield Guide: Normandy Landing Beaches.
Hope this might help (a bit)!