Although I can't speak for Carnival ships, I thought I'd share some of the odder places that we have found the dart boards on ships, so whilst Cunard quite sensibly have them in the Golden Lion bars, Fred Olsen have one on a lower outside deck right at the back of the ship, so that you get every movement as the ship pitches & turns which makes for an interesting experience, and another line had theirs in the Ironing Room !!! Okay it was a large ironing room and it also housed a ping pong table, but still made up smile.
Hope you are able to find one, if not, the balloons used for celebrations could be in for a bad time
Last Cruise: Queen Victoria November 2014
Next: P&O Britannia March 2015
Then: Minerva April 2015
and : Royal Princess August 2015