Trip insurance for short cruise is likely really minimal and always worth it for peace of mind:
http://www.cruisedeals.com/clients/travel_insurance.asp
Another type of bag insurance that our TA (Jennifer at All Aboard Travel) recommended is ony $5 per checked bag and guarantees a check for the full bag replacement value within 48hrs of luggage missing is something called blue ribbon bag insurance.
It was well worth it for a recent Europe flight where 1 of our luggage pieces did not make it to our river cruise departure same day, so we had a check in 48hrs via express mail and were able to buy clothing for the bad weather.