You might be thinking of the Tambu Lounge, which has a small food menu. The quick service is Capt. Cook's, and there's a grab-and-go counter called Kona Island. The table service Kona Café may have walkup availability or room for a last-minute ADR (more likely than 'Ohana, anyway).
We were there for the second half of last week (Wed 3/9 to Sun 3/13), and of these, my favorite was mobile ordering from Kona Café. In the app, it's Kona Café to Go: You essentially get table-service food to go, and you can eat it only steps away in the seating area outside Tambu (or take it outside, or back to your room, or wherever). We didn't try to get a table, so I don't know how difficult it would have been, but mobile ordering suited our needs perfectly well. If you prefer to try for a table at Kona first, you can still keep the mobile option in mind as a backup plan.
One note: Either the mobile ordering menu is missing a couple of things that the table service menu has (specfically, the dashi bowls, which they might not have a good way to package for takeout), or they were just out at the time we ordered. Since the only plant-based entree on the menu is one of those dashi bowls, that might have been an issue for a vegan or vegetarian eater (the menu is mostly sushi or meaty sandwiches). But otherwise, it was a nice option and worked really smoothly.
Additional casual food options include the pool bars and the Tiki Terrace (or Trader Sam's, if you can make it in). The Tiki Terrace started serving at 3 when we were there, and they had a small food menu. The pool bars serve food until 8, and we had a fantastic salad. Much better than we expected at a pool bar.