I stayed at the Sheraton Keahou for 5 nights in March. Overall we had a good stay. Only real downside in my opinion is the lack of a beach on hotel grounds and the food wasn't great. It is a pretty spot though, and the manta rays are supposed to be very cool...if you are around just after sunset (and they actually come out.) You can get quite a few more opinions
here.
We met the the owner of country samurai coffee at his shop a few miles from the hotel (in Kona Square just off of Alii Dr.) and really enjoyed his coffee.
http://www.countrysamurai.com/
The owner (Walter) was a really nice older man who took time to tell us about a bunch of great spots and marked them on a map. For a tour of a Kona coffee farm he recommended Greenwell Farms, which we did check out.
http://www.greenwellfarms.com/
They give a free short tour and are very friendly. No sales pressure or any B.S.
Also nearby you should also check out Kona Coast Macadamia Nut & Candy Factory.
http://www.konaoftheworld.com/index.html
Not as friendly as the Greenwell crew, but these guys (also a recommendation from our Samurai friend) do in fact roast one of, if not the best macadamia nuts you'll find. Just make sure to buy the ones in the vacuum sealed packs (8oz I think). The dark chocolate macadamia bars are also worth a try.
Driving south from the hotel we had a nice lunch at
coffee shack. The view is great from the small lanai (
my photo.)
A bit further south down the road is
Kaloko-Honokohau National Park. Some interesting ruins and we got to see several Honu (green sea turtles). (
My friends at the park.)
Regarding the Mauna Kea summit, it is worth it if you are a fan of stargazing. We went on a tour
(Summit and Stars) with Hawaii Forest and Trail and had a great time. Our guide Greg was fantastic and he shared tons of history on the island. He knew all of the plant and animal species around which he pointed out along the way. And after a quick dinner (average) and a windy ride to the top for a nice
sunset on the COLD summit you return to the visitor center (a couple thousand feet lower) where you get an in depth tour of the night sky on their scope, along with some hot cocoa and fresh baked cookies. The last time I saw a sky that clear with so many stars I was in a planetarium. We saw satellites and shooting shooting stars...along with various planets and constellations. Greg really knows his way around the sky. If that sounds appealing to you I highly recommend you try it. But it may make for a long day for an 8 year old.
And if you are up for a drive, I'd recommend heading to Volcano for a day. It's about 100 miles from the Sheraton. Check out
Volcano National Park. The crater was
smoking pretty good when we were there. There are some closures as the volcano has been active lately, just recently flowing over a small highway. I believe the seaside viewing location (a good ride from the park) is closed at the moment...we saw a
lava flow there.
While you are there have a meal at Thai Thai. Definitely the best red curry I've ever had. Just make sure you don't order anything hotter than medium, if that!
If you continue east and visit Hilo there are a couple of nice waterfalls to see (Rainbow Falls and Akaka Falls.) And while you can skip the tourist trap Mauna Loa factory I do recommend
Big Island Candies. Lots of cookie and coffee samples. Towards the back there's a counter that sells reasonably priced ,and tasty, ice cream (we got Mango flavor.)