Hahah, well said Voolf!

You could have a look at this map of the Millennium Falcon, Mouse. Not an island like yours, but it does have both a legend and labels on the map itself. In this map they lave put the rooms in the legend, and different part of those rooms as labels on the map. You could do something similar. Perhaps you could put the 'regions', like Screaming Point, on the map as labels, and have building, structures and caves etc. in the legend. Or the other way around, whichever doesn't look ugly as hell!

Hope this is any help