I'd suggest Kona as it's a non-stop flight from Seattle and around $300-350 in June. Some of the other islands are also but it's just an easy 6hr option. You land at night but there's literally only one main road north or south to the resorts. Cabs are prohibitive though so rent a car. Plus you can use it to shore dive later in the week since those sites are pretty spread out also - it's called the Big Island because it is.
love good photo opportunities, big creatures etc. any suggestions?
Like this?
[video=youtube;d24LR0BeILQ]https://www.youtube.com/watch?v=d24LR0BeILQ[/video]
This dive regularly makes Top 100 dives on the planet lists.
If you spend a few days boat diving south with one of operators it's pretty likely that your dive companions could be the Spinner Dolpins that frequent the area. My buddy had an escort once - the DM estimated them at 500 or more. All just 20' away - some even passed between them. It is lava substrate diving so the animals have learned to hide better. So hiring a good guide is not a bad idea.
On a non-dive day there's also:
Hawai'i Volcanoes National Park (U.S. National Park Service) More of a drive than it looks on a map plus it's around 4400' also IIRC. One thing to be aware of especially on Kona is that once you move even just a few miles inland you're driving to elevation. Were you to trek over to Hilo one day, the Saddle Road peaks at 6600' - Mauna Kea over double - 14,000'
In Kona (actually Maui or Kauai also) in June I'm diving in a t-shirt. The only time I might wear a skin is to get over the lava at some of the Kona entries - they're rough.
On Maui they're beaches or on Kauai the only two shore dives worth doing are Tunnels Beach or Koloa Landing - which is a ramp. For really big turtles - Sheraton Caverns is a boat dive there with some huge turtles. The Sheraton is actually not a bad base either - they have their own boat and are in Poipu Beach where many of the other dive operators with boats base their operations. Koloa is just down the street also.
Maui should be considered also since there's arguably more diving there. There's the most shore dives along the west coast, almost all easy beach entries, diveboats based in Kihei dive the famous Molokini Crater, dive boats in Lahaina dive Lana'i where the signature dives are the two Cathedrals. Depending on weather, Lahaina Divers also runs all the way to Molokai looking for Hammerheads once a week. If I was trying to do as much different diving as possible in a short time, Maui would be a consideration. Basically any of the waterfront resorts in South Maui are located on beaches that are also known dive sites.