last time we ate breakfast there, we were told breakfast was from 7:30-10:30 AM.
One suggestion...if you've never had tonga toast, save yourself a good chunk of change and just get it from the Polynesian counter service place (Captain Cook, located on 1st floor of Polynesian.)
When we tried tonga toast, we got one order and even splitting it between 3 adults we did not finish it because it was so sickeningly sweet. Ordinarily, we all have a really sweet tooth, but hot-slimey-bananas in sugar coated toast...well. Needless to say, we did not like it, lol. We were really glad we'd paid about $4 at the counter service. Think it's $8 or $9 at Kona Cafe.
Our favorite breakfast at Kona is the Big Kahuna...easily large enough for 2 adults to split, and it comes with the luscious macadamia nut butter on the pineapple pancakes. There's some good eating.