Give IOA a try. The themes of the various lands are as good as it gets in any theme park, and the rides and shows are fantastic (don't miss the Spider-Man ride, Jurassic Park River Adventure, or Posiedon's fury).
Since you are going to 'Ohana for dinner that night, I recommend a light counter-service lunch. IOA has several excellent choices in this area; I recommend either the Enchanted Oak Tavern in the Lost Continent, or Thunderfalls Terrace in Jurassic Park. Either will give you an excellent meal.
When leaving to go to dinner at 'Ohana, leave the park gates no less than 75 minutes (1-1/4 hour) before your ADR. It takes 10 minutes to get to your car, then another 5-10 to get to I-4, and about 25 minutes to get to Polynesian once you get to I-4. Total time from IOA gate to Poly is about 45 minutes, but you want to give yourself some leeway in case of traffic. If you arrive at Poly early, check in anyway and have a look around the lobby.