There is several restaurants onsite and more on that attached shopping area. In Waikiki most of the restaurants are chains, but still good eating.
Now the Grand Waikikian is not really on the strip with the rest of Waikiki so just remember that you are going to walk a little bit to get to the normal shopping areas/dining areas around the other hotels.
At the Grand Waikikian there is a restaurant that opens up to the beach under one of the towers and has pretty good food and nice views. Might be a little pricey, but Hawaii can be that way.
Duke's is usually where everyone wants to eat at least once. Depending on when you get there it can be a pretty good wait, but there are shops around to kill time. Also there is sort of a sister restaurant upstairs from Dukes' that almost has the just about the same menu is usually less crowded. Duke's is in the Outrigger on the Beach, do not get confused with Outrigger on the reef. Very close to each other, different hotels owned by same people.