Tiger does not come with any stuffit utitlities but does come with the ability to decompress GZ natively, so switching to TAR.GZ would be a good idea.
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
Also a short readme could be added to the disk image with some simple instructions taken from this site, with links etc inside.