Bluegills and bass are a better idea in a small pond. One balances out the other. To keep the crappie from over populating, you need to remove lots of them after they've spawned a few times. Florida strained bass will help if the pond is big enough. Catfish too.

D-10 is the best resource for the correct way to manage your situation. If he doesn't know how to do ponds, I'm sure he can direct you in the RIGHT direction. Good luck on the sale of your place.