If the Ghost shrimp are labeled as Palaemonetes paludosus, or just Palaemonetes, which is actually an American species, the Eastern Grass shrimp, then they should be safe enough with cherry shrimp.
It is true that the adults will eat very young cherries if they catch one, and it's not all that easy for them to catch them. Ghosts also eat their own very young shrimplets, but so long as you provide lots of hiding places, such as thick plantings, rocks or wood, the majority of the baby cherries will survive just fine.
I've kept these two species and a few others all together, along with a number of fish that might well have been expected to eat baby shrimp too, in a 29G, and the cherry shrimp colony grew steadily. I'm sure some of the babies were eaten, but not enough to stop the colony from growing.
Unless you are trying for maximum numbers of cherry shrimp babies, they should do ok with Ghosts, provided it's the right Ghost species. There are at least 3 species sometimes called Ghost, but the one most of us in North America think of when we see this term is the Eastern Grass shrimp, which is native to the south eastern USA.