congrats. lots of fun, lots of hard work.
Oahu is expensive and crowded, but fun can still be had. Diamond Head, North Shore, several cool forest preserves and botanical gardens, etc. just depends what your version of fun is i guess. i always stayed in Waianae when i went because of the military rec center. $20 a night for a bungalow on the beach was hard to beat.
a trip around the island if you have a rental car, lots of off the tourist path places to visit, lots of local culture to be had. the rental car map used to show the 93 ending at the north end and lots of 'not covered if you go' stuff on the map and in the car. i went, spent the afternoon at the point, then went east until i was back on road, 930, and back through North Shore. not recommending breaking your rental contract, but was an amazing day and memory. Pearl Harbor was epic, highly recommended. food is expensive everywhere, picnics are cheaper and more fun than restaurants in my opinion and the weather is always good to go. take or rent a boogie board, Everywhere is good! if you surf, ignore the previous recommendation, and Everywhere is good! North Shore on a bad day is better than everywhere else in the US 99% of the time. Waikiki once is a must, you have to take the tourist photo by the sign. All around the area there are lots of evening Lua shows if you run out of other ideas. cheesy, but good music/food, usually a free shell necklace to bring home, and then you can say you've done it once i guess.
loves me some Maui. although i've been to them all, i keep going back to Maui. just like Oahu, lots to do depending on you two and your version of fun. things i would recommend, the snorkel trip you already listed, the Maui Ocean Center over near Maalaea Harbor is awesome, Haleakala National Park is totally worth the drive (how often do you get to hike inside a volcano?!), there are several hour bike trips you can book where they drive you to the top of Haleakala and then you bike/coast down. awesome if you like biking, usually end up in Pukalani or Paia depending on how long a trip you booked. both have lots of local restaurants and cool places to hang out, local art shops, local flavor with a touristy edge. fun stuff. i spent morning, new years day 2001 watching the sun rise over the rim of Haleakala wearing every single piece of clothing i brought, wrapped in a trash bag, and still just about froze to death... would totally do it again, epic memory/experience. just for fun, it's pronounced Hall-lay-a-ka-Lah with and emphasis on the first H and last L. sound local brah for the win! Wailea/Kihei is my favorite area to stay on the island. Kahului you have to see because of the airport, Lahaina/Kapalua is the touristy trap on the island and can be avoided (nothing worth seeing) unless again you are doing the rental car loop on the 30/340 for the amazing scenery and local flavor. Iao valley is amazing and not to be missed if you like hiking or taking photos. we stay in Kihei (Key-High) at a B&B when we go. my favorite thing to do is walk down the hill to
Hawaiian Moons natural food market to get a big ass salad from the in house salad bar and a couple of brews, and then walk across the highway to Kamaole Beach Park to sit on a bench and watch the sunset, waves, and whales. very nice beach/park, fresh/cheap food (less than resturants), and free entertainment is my idea of fun and relaxing. there's also a Maui Tacos in the same strip mall which is also tasty and reasonable compared to other places in the area if you're into fresh mex with an island twist...
i would not recommend the road to Hana based on personal experience. my wife gets motion sick on tight interstate on ramps or in parking garages with tight/sharp turns for perspective... did the Hana road one time, regretted it, won't do it again. 2 lanes (or less), twisty as hell, driven by locals going 10-30mph over the speed limit and bent on killing you or just running you off the road, either is fine with them... Hana itself is amazing, Waianapanapa State Park with the black sand beach is totally amazing. on our trip, after finally surviving the road, i had to stop in Hana to let my wife recover. after several hours of laying under a tree with eyes closed and breathing deep, we went south just to avoid going back on the Hana road. took the 31/330 around the edge of the island which is/was another 'don't go here with a rental car' road that will eventually drop you back in Wailea. no stops, no support, no gas, proceed at you own risk, beautiful drive if you survive... i remember stopping at 7 pools and a historic mission/chapel as well as not to be believed (if i didn't have the photos to prove it) views and scenery.
sorry for the ramble, good memories make it hard to be brief. best of luck to you both.
