The Infinity has a "casual dining alternative," which is a phone-ahead sit-down venue in the Oceanview Grill area each night. It allows you to work around shore excursions, or take a respite from the main dining room. We used it a couple of times and enjoyed its flexibility. The menu is limited, but good, the service is excellent, and the convenience is worthwhile. We were able to get a table whenever we wanted, but the dining room and specialty restaurant food and service are so exceptional, there are few reasons to miss it, unless you are a tie-phobe and want to avoid dressing up.
We very much enjoyed the concierge class amenities on our 14-day Hawaii trip. For a shorter cruise, I am not sure I'd pay the extra for what you get over a regular balcony cabin (which CC cabins really are...)