I could care less about seeing Waikiki beach
You may be pleasantly surprised! Waikiki is quite a different area than anywhere else in Hawaii. A lively atmosphere, fun vibe. Great place to people watch. We didn't spend time on the beach there, but still enjoyed strolling the strip and dinners on the ocean. They also do fireworks on Friday evenings on the beach near Hilton Hawaiian Village.
But no way could I stay on an airplane for ten hours,
We flew from Atlanta and it was roughly 9 hours. I was concerned about the length of time as well, so I researched which airlines, flight numbers, and flight times had aircrafts that would be most conducive to keeping us comfortable. We booked standard coach on Delta's nonstop out of Atlanta and the flight was on an Airbus 300 and had a 2-4-2 seat configuration. This gave DH and I our own row. It also included free alcohol, hot meals, unlimited snacks and drinks, and each seat had its own seatback TV with hundreds of movies, TV shows, music, and games. The flight attendants all wore leis and had pillows in each seat. There was also a power outlet at the seat where I could plug in my own device. Having these luxuries, even in coach, really helped pass the time. It wasn't nearly as bad as I thought.
Alternatively, rather than spending money on a hotel in California, you could use that money to upgrade to another level on the flight like Comfort+ or First Class, depending on which airline you fly.
Plus I want to take Hawaiian airlines to Hawaii. Do they even fly out of Atlanta?
I believe Hawaiian partners with JetBlue. So you'd fly JetBlue from Atlanta to JFK (most likely) and then connect on a Hawaiian Airlines flight to Honolulu. Since they're partnered, it would be seamless to you as if you're flying the whole way through on the same airline. They will still facilitate transferring luggage, etc.
Why Hawaiian Airlines? Coming from Atlanta, you'd be going backwards to JFK and I believe a JFK to HNL flight is longer than a ATL to HNL flight. As I'm sure you know, Delta's main hub is Atlanta and their nonstop flights would likely be the shortest time, unless you want one with a layover. Keep in mind that a layover makes the total travel time longer, even though it breaks up the flying time.