Hi Chris,
You do have a lot of options!
Going by the fish I have that my kids love the best, I'd recommend; Bristlenoses (I saw that you wanted a sucker fish; be careful as some of them grow to the length of your tank!; the bristlenoses grow to only 4 or 5 inches; they'll probably breed as well if you can get a pair), livebearers like swordtails, platys, guppies and endlers (just try and get either all males, or two females to one male if you don't mind them breeding) and the hardier dwarf chiclids like apistogrammas or kribensis.
All of those a relativly easy to keep and are not too fussy about pH or hardness and most of them have the possibility of breeding for you (well, if you have livebearers, you won't be able to stop them!)
I'd totally back up mattlee's advice not to have any kind of Ram; they are extremely delicate (some people consider them more difficult than Discus!)