Personally I think 'Ohana is too busy and family-oriented for an adults-only night out. I'd go to The Wave at the Contemporary, Wolfgang Puck Cafe or Raglan Road at Downtown Disney, Tutto Italia at EPCOT (although it can be pricey) or San Angel Inn at EPCOT.
Of course there's always the California Grille at the Contemporary, Narcoosee's or Citricos at the Grand Floridian and the Yachtsman Steakhouse at the Yacht Club, but they are all quite pricey. Since you're looking for something a little less expensive I'd go with one of the first places I listed, with The Wave and Wolfgang Puck Cafe being my top two choices.