A lot depends on how many rabbits you have and what you are doing with the kits. If you have purebred stock and are breeding for sale or show, detailed records are very important. If you just have a handful of meat mutts, providing some meat for your table, you should still keep records, but a casual jotting in a notebook may be enough.
I have an "everything book". Anything I want to keep track of about any subject from an email address to when I bred the rabbits gets jotted down in there. Works for me. My idea of a note about breeding the rabbits would be along the lines of "Alice to Jasper, July 20/10". I do have a more detailed anecdotal account of what is happening in the rabbitry and I keep this as a WORD document, but I admit I've let it lapse rather badly.