One tip:
Check out Google.com/flights
Type in your info and select Delta or Skyteam. It will show you fares across the entire calendar and you can select the days with the best fare.
I used this last summer for a D1 flight to Europe and got a great fare.
One issue you will run into is flights to Hawaii are a leisure route. Fare sales on those legs are tough. I go the Caribbean twice a year and I have never found cheap F tickets in 4-5 years of buying tickets. I usually buy F or K+ and use UG certificates. Most F tickets are over $1k. In comparison I'm going to Seattle in two weeks and my RT ticket in F from DCA was $700.