I would ask over on cruisecritic. I think you'll have enough people over there who have cruised on Vision *recently* that someone will know. I know that on freedom they have a softserve place on the pool deck, but I don't know for Vision.
But, given our ingredient issues (all American softserve has corn syrup-based sweeteners, and we can't have that), we found that upping our budget for the safe flavors of Ben & Jerry's worked out beautifully.