Your labs may not be too interested in peas, at least mine aren't, the other mbuna all love them. But if you squish them really good they might try them.
Most Mbuna will take peas but it is essential that you remove the shell as they will be unable to digest this properly and it could easily lead to Bloat/digestive problems. Labs tend to eat insects etc in the wild so may not be as interested as other Mbuna.
My labs have thwarted any attempt I have made to establish a snail colony of any type in their tank. They can't crunch shells but kinda suck em out so no harm done I think.