Idealy as you have a package installer anyway, a DMG diskimage is the OS X way to handle these things, its compresses has a checksum by default, if you really want you could go the extra mile and have a DMG.gz but it serves little purpose
![Smile :)](./images/smilies/icon_smile.gif)
Also a short readme could be added to the disk image with some simple instructions taken from this site, with links etc inside.