Some of the best food you'll ever have is this place:
https://www.tripadvisor.com/Restaur...rant-Kailua_Kona_Island_of_Hawaii_Hawaii.html
Let me tell you that any reviews on here that say it wasn't excellent, those people are morons who don't know good food and a nice meal. This is French cuisine and I've never had anything there that wasn't perfectly cooked. Small place, maybe like 6 or 8 tables, owned by a wonderful couple. They take great care of our family any time we're there. They cook and serve everything themselves. You would definitely need a reservation. This is a nice meal we're talking, so if going to expensive restaurants makes you uncomfortable just don't go.
Tell your bank you're going to Hawaii. I got to the checkout at the grocery store and my card wouldn't work because evidently BofA can't connect the dots when you use your card to eat at a string of airports and then a day later you're in another state. Also there are no plastic bags there, so either bring reusable bags to the store or you'll have to buy bags.
There is a boat tour called The Fair Winds that is a lot of fun...but not with a hangover. Wife and I scheduled that for New Year's morning and we "fed the fish" off the back of the boat for the whole ride to Kealakekua Bay. So don't drink a bunch of margaritas the night before and you'll have a good time. They serve fruit and muffins for breakfast while you ride out there, then you snorkel, you can dive off the top of the boat, there's water slides. You can do "SNUBA" which is like SUBA except the tank is up on the surface in a little raft you pull around with you and you have a long air hose. You only go about 20 feet down and you don't have to be certified. Lots of fun.
https://www.fair-wind.com/
Hapuna Beach is excellent, huge with soft sand, bathrooms, showers. Bring a cooler and make a day of it. It's about 40 mins to an hour drive. Check before you go to make sure it's not closed for high surf or anything. Good place to go boogie boarding.
One of the resorts north of town near the airport has a FREAKING AMAZING buffet. It'll cost you at least about $40 a person, but fresh fish and seafood like no other, plus any other kind of breakfast food you could want. I think it might be the Four Seasons but I'm not 100% on that.