Your plan is commendable, but depending on supply and demand, part b of your plan can prove quite variable.
We were on the MV of the Fantasy and O'Gills was kicking kegs left and right. The Guinness was gone by Tuesday and most of the micro brews were gone by Thursday. They were down to a few kegs of Kona Longboard by the end of the cruise. The bartenders said
DCL based their demand numbers for O'Gills on the average consumption numbers at 687. O'Gills proved to be far more popular than 687, as it was packed every night. We were on the Dream about 6 months before the Fantasy MV and 687 was a ghost town. We were on the Dream again in January and not much has changed.
Other bars on the Dream sometimes changed beers as kegs ran out.