You a predator heavy already, adding crappies will most likely cause more problems than solutions. I would removed 50% of your walleye at a minimum.
Crappies can be successful in small ponds, but you have to really work at it. Either many stunted LMB to help control crappie reproduction and even then, it's no guarantee. The heavy use of traps to trap and remove crappies along with high fishing pressure on them. Or pray you have one of those 1 acre ponds that just seems to never produce a good crappie spawn. I have seen a number of small ponds that just couldn't pull off a successful crappie spawn, but a number of different reasons. Then you just maintain crappie number via stocking.
