Tried all the islands in the last 40 years and settled on Big Island. Just fits me, a lot less touristy the most other places. Funny the majority of people come over and stay at the big resorts. I meet people that never want to leave their beach chair. More power to them.
My suggestion is Kailua town. Beach (small), about 40 watering holes. The bars are a great mixture of locals and tourists, make for a great feeling.
All sorts of water adventures (been on most of them numerious times with guests). King Kam has a very upscale spa.
A couple of locals type golf courses (Pete Dye designed) that even as a "guest" you can get on for about $60.
Enough, I love it here.