Or if you really want some crappie you could try out the hybrid crappie and keep track of them for us in that pond. I think if they do not spawn as much like they say and the offspring is inferior then you may grow out some large initial stockers and not ever have to worry about the over population of small critters. (then again studies are still being done on them and a few people here have tried them)
I would actually put in a few Blue Cats and maybe even a Flathead. (not really recommended by most)
That was just my $.02 and wanted to throw it out there.