Fishhead -- Bob Lusk always says to manage the habitat first. If you can afford an aeration system, I sure would do it. What is the value of a 2.5 acre pond? That is a darn good size pond, and with high water quality, what a resource it would be.
Now my 2 cents worth. I agree that crappies won't control bluegill. Also, crappies winterkill rather easily, too. If you decide to aerate, get the LMB established. Then, we can talk about crappies. If you have the habitat, and your coontail says you do, then you'll get a high density LMB population. Not everyone will agree here, but at that point, you'll have enough LMB to control reproduction by both bluegill and black crappie, and you can produce 8-10 inch bluegills and 10-12 inch black crappies (few LMB will exceed 15 inches, but in a 2.5 acre pond, a few will always slip through the bottleneck to larger sizes).
