NCL has a program called Dine Ashore for its Bermuda Cruises. They issue coupons for lunch, at local restaurants. For an additional charge, the coupon may be used for dinner.
My suggestion is, extend this program to other cruises with overnight stays in some ports. For instance NCLA ships overnight in Maui. Bring the program to Hawaii. It would entice cruisers to try the local restaurants, for the price of the coupon.