My husband and I stayed at the Mokolii Beach House for our honeymoon, and we couldn't have asked for a better experience! Having the sand and ocean literally RIGHT in your backyard is nothing short of Paradise. The house was perfect for us, and stocked with just about everything you can think of. I'd recommend checking out the house before you go grocery shopping. My husband and I got plenty of use out of the kitchen by making every breakfast at the house, and most dinners. Debbie was very welcoming, and a great resource for any questions we had about the house or the island. She even gave me a piece of the aloe plant in her yard to help my nasty sunburn! Sasha was also very accommodating with prompt responses to email, and thoughtful answers to any questions we had.
Here are some of the activities we enjoyed on the island, that I would recommend to future travelers:
1) Seriously, just spend a day at the house! Put on your favorite music (there's a nice bluetooth speaker - we did this just about every day!), and just relax!
2) You have to take one of the kayaks out (there are 2 singles and 1 tandem). Chinaman's hat is a quick, easy paddle. We packed a cooler and spent the whole afternoon exploring! Just ask Debbie where the best place is to beach the kayak. You can hike to the top, but be prepared with adequate footwear, and know that some paths are better than others.
3) Some of the best snorkeling is at Hanauma Bay. Pure Aloha Adventures has small tours, which I would HIGHLY recommend. Your guide provides all equipment (including float belts for those less comfortable in the water), and teaches you the basics of snorkeling before heading out. The best part was that our guide knew EXACTLY where to look for sea turtles, octopus, eel, etc. We used an entertainment coupon so it was reasonably priced! http://purealohaadventures.com/.
3)Hike up Diamond Head for gorgeous views! We saw people of all ages that could manage this hike. Just bring water and sunscreen, and a good pair of shoes!
4) For the adults who like to party: do a booze cruise! We did one of Tom Barefoot's Tours, a sunset cruise on the Holokai Catamaran, and it was a blast! https://www.tombarefoot.com/things-to-do-in-hawaii/island/oahu/3.
5) Kualoa Ranch. The other reviews have pretty much said it. Highly recommend!
6) Take a day to explore the north shore! We stopped at several beaches (Malaekahana State Recreation Area & Goat Island, Turtle Bay, Banzai Pipeline, Waimea Valley & waterfall).