I have not yet tried photographing small animals yet, but the lenses recommended in this thread are good, the Canon 100mm is a cracking lens. Also the Sigma EX DG's are good,and cheaper than Canon's... may be a zoom macro by Sigma may be a good buy, as you have the flexibilty with the focal length(zooming in and out without having to move the camera), and if you want a close up of eyes etc, the macro will focus really close.
May be try a well polished pane of glass instead of the mirror, it may give a slight reflection without being too distracting if you don't fancy heavy editing in photoshop, which it sounds like you don't
ps- may be after some advice on photographing snakes etc very soon from you guys in the photography section!!
Has anyone tried the glass, let me know how you go!
regards Scott