I haven't had much luck with emerald crabs. Not sure why you need them unless you have bubble algae. Some people say they eat hair algae. I had a tank full of hair algae and the emerald crab didn't touch it.
Cerith snails are good snails to have. They clean the glass, sand and rocks. If they end up on their backs they will flip themselfs over. (That is some thing turbos can't do.)
My favorite sand cleaners are fighting conchs and a tigertail cucumber. They keep the sand white.
Why do you want peppermint shrimps? To keep any aptasia from spreading?