Using Basic Building Blocks a basic layout can easily be put together on any flat surface of almost any dimension. The larger the display and the more variety of blocks the more interesting your town will become. So long as everyone has included the correct streets minifigs should be able to get anywhere they need to in your town.
Because this is a pirate-themed display you will need to create some form of shoreline. A beach or rocky shore can be created using blue baseplates which will also allow you to create some form of Dock if needed.