brim are good, crappie i would get rid of, they will also compete for food with your bass. Easy trick if you ever want to remove almost all of the crappie from an area is catch one and then run a hook in his top fin and run 4-5feet of line from it to a cork or bobber and then throw him back, crappie are a schooling fish so once he goes back he'll look for the rest of the school and start swiming with them so once he calms down you just look for the bobber and keep hitting that area, you'll catch them so fast you wont believe it.
Grass carp are great for keeping weeds down but they wont do a huge amount when it comes ot the banks but thats actually a good thing as you want you banks to be good and planted so you dont loose them to erosion. (and for your lake i wouldn't recommend anymore than 2-4 carp. ) let me know if you ever have any questions about this kinda stuff, did pond management for a living for years so have lots info im happy to share.
