Oh! I was just there last October and have a lot to add here, but I'm out of time at the moment. I'm posting here so I don't forget to come back to this later! :)
Crap! Guess what I forgot to do; hope I'm not too late here!
So we were there for 4 days and did a lot, but still had some nice downtime too. We took one day to make a big loop around the whole island. Now this was a full day; leaving the resort by 7 AM and not getting back until 8 PM, but it was totally worth it. We were staying on the Kona side, so this is a big clockwise loop around the island. Things we did along the way (I would add my pictures here but those are at home, on the home computer...):
Waipio Valley Look Out - It's worth it - awesome view and worthy of some incredible photos if you do photography.
Akaka Falls - Another must see. Breathtaking. Camera required!
Hilo - worth driving through and stopping for a bit if you're staying on the Kona side. We were told to hit Rainbow falls just around the corner, but we did end up skipping that.
Volcanoes Park - Sounds like you have this covered. You'll have about a 14 mile hike to actually see Lava though. We spent a few hours in the park and saw 4 of the main attractions.
Punaluu County Beach Park (blank sand beach) - Worth the stop. Beautiful and a good chance at seeing turtles near the center of the beach. And you'll find the Nae nae goose near the ponds at the east end
South Point - One of my favorite sites there, but it's a bit off the beaten path for sure. Don't try to take a rental past the end of the paved road; just pull off to the left where the asphalt ends. The actual south point is just past the blinking light and straight inline with the stone wall that's there. Most people mistakenly think it's the cliffs off to the right. We were here around sunset and it was amazing. The surge and the surf was incredible, each a good 10-15 feet! (and not some place you'd want to get in the water)
We already have a significant amount of time planned in Volcanoes National park.
I'm sure you've done the research, but I would have loved to have done the Iki Trail had we had the time.
I'm planning on looking for excellent photo opportunities as my main focus while there.
Good. :) See those notes above then.
Obviously we'll be doing some snorkeling
More on this below.
I wish we had time to check out the Waikiki Aquarium on Ohau, but it will have to wait until next time.
Heh, we spent 2 days on Oahu before heading to the big island, and this was the first stop. As a fish guy, it was overwhelmingly awesome!
Do not leave big island without doing Mauna Kea. It's like going to Mars, it's wild. You'll need to rent 4 wheel drive if you want to do it on your own.
Agree! This was something else we did, and it was probably my 2nd favorite thing. We didn't rent though, we booked a tour with this company (and would certainly use them again):
http://www.maunakea.com/
The sunset was beyond fantastic; take the camera again!
I don't know how things are in the winter, but snorkeling in Kahalu'u Beach Park during the summer was a lot of fun. Great variety of fish.
So I wanted to spend more time snorkeling, but a half day was all that happened. My partner had never done such before, but I knew he'd be okay after a bit. And he was, but we both got really sunburnt. Trying to be reef conscious, I had picked up some coral safe sunscreen ahead of time - it doesn't go on easily nor does it stay on well apparently...
Anyhow, Kahalu'u is where we went, and I'd recommend it as a good starting place. It's rather shallow and teaming with life. And yes, I saw a Koi yellow tang as well. :)
I would recommend going to Hanauma Bay State Park, awesome snorkeling. There is an entrance fee but worth it, you can park and walk-in.
http://hanaumabaystatepark.com/
But this is where I really wanted to snorkel; two steps! (as it's known) I was a bit heartbroken we didn't make it here.
Apparently, snorkeling in Kealakekua Bay near the Capt. Cook Monument is some of the best on the Big Island, but getting there is a little tricky. You have to hike or kayak in to the bay.
I saw a lot of mixed reviews on that location, and ultimately I decided two steps would be all around better.
There are manta ray night snorkels in Kona. I never went, but they are very popular.
YES! We did this, on the evening of my birthday. I booked through Kona Ocean Adventures, and it was worth every single penny. My favorite thing we did by far, and a life time memory. We literally had an adult Manta doing feeding roll within an inch underneath us. If you're going to spend a bit of cash on any one tour, just do this! I left the camera at the hotel this night, and in many ways I'm glad I didn't have it as a distraction from the experience.