The subject has come up on MMM's blog, with some of your questions answered in this post:
http://www.mrmoneymustache.com/2013/01/07/second-hawaiian-meetup-this-friday-waikiki-beach/More links to other MMM posts at the bottom of his summary post:
http://www.mrmoneymustache.com/2013/02/10/the-hawaii-project-final-numbers-and-a-few-pictures/You can use the search results from this page:
http://www.google.com/cse?cx=partner-pub-6888579577133851%3A2423690505&ie=UTF-8&q=Hawaii&sa=Search&siteurl=www.mrmoneymustache.com%2F&ref=&ss=719j89829j7#gsc.tab=0&gsc.q=Hawaii&gsc.page=1You've set a tough standard by your spouse presenting at one of the island's most expensive locations yet wanting to get a frugal trip out of it.
Since you have a little time before you fly, you could try posting your questions on HawaiiThreads.com. It has a very busy section of people asking about moving to or vacationing in Hawaii, and a lot of the board members live to know it all share their experience. You'll get a lot of kama'aina recommendations, and you might even find rental home bargains that you'd never see on a consolidator's website.
Ideally your spouse could get comped or discounted lodging at wherever she's presenting. If that doesn't work then take a look at:
http://www.cyberrentals.com/USA/Hawaii/Oahu/r245.htmAirBnB
VBRO.com
Travelocity
Priceline.com
You're arriving at the end of the high season, so landlords aren't desperate yet. I'm not sure that you'll find many discounts, especially if the snowbirds are loitering here until Mainland spring really gets started.
Waikiki lodging is relatively safe but some is noisier than others (traffic, karaoke bars).
For activities, start with the "101 Things to Do" website and pick Oahu.
http://www.101thingstodo.com/I've set up my blog with a 3D Travel widget that uses Google Earth to "fly" around Hawaii. It's pretty realistic:
http://the-military-guide.com/2012/10/29/3d-hawaii-right-here-on-the-blog/Note the "HulaCopter" logo for some locations which offer major discounts on last-minute activities. You can stalk your chosen entertainment on your smartphone to see if you can get 30%-70% off for being able to jump in at the very last moment. Of course this also requires transportation and a Plan B.
You're probably expecting to do this trip around Waikiki. Hanauma Bay, the Diamond Head Lookout hike, & Makapu'u Point whale-watching are right around the corner. (Hanauma Bay is closed on Tuesdays.) There's Sea Life Park, the Polynesian Cultural Center, and plenty of shopping/browsing. Waikiki even has a zoo and an aquarium, which are surprisingly good for their age & location. The airport baggage claim is stuffed with flyers and activity calendars like "This Week Oahu".
http://www.hidili.com/thisWeekPublications/thisWeekOahu/The most convenient public BBQ for you is probably the park just Diamond Head of the Hilton Hawaiian Village. (Site of the last MMM meetup.) It's set back from Kalia Road by a few hundred yards, behind the Hale Koa Hotel. Supplies are available at ABC stores (one on just about every block in Waikiki) or you could take Da Bus to a grocery store.
Bus schedules are at
http://www.thebus.org/ , and there may be smartphone apps that use the API behind this utility:
http://hea.thebus.org/I would not ride a scooter around Waikiki, even with body armor and a helmet. Too many drivers are watching too many other things to pay any attention to you.
Depending on how much snorkeling you plan on doing, you might want to stop by Wal-Mart now (before you leave) to buy a mask/snorkel that makes you happy. Fins are "nice to have" but not essential. Otherwise you could rent just about any beach gear from one of the concessions on Waikiki Beach.
If you can swim then you can surf. Even if you can't swim, the lifeguard can probably still teach you:
http://the-military-guide.com/2011/03/28/lifestyles-in-military-retirement-learning-to-surf-in-hawaii/http://the-military-guide.com/2011/08/29/lifestyles-in-military-retirement-surfing-photos/If you come out to the USS ARIZONA Memorial (the #1 attraction on Oahu) then plan to make a day of it. Don't use a tour provider, although there are many of them. Instead book your reservation at the Memorial through the NPS:
http://www.nps.gov/valr/planyourvisit/feesandreservations.htm and travel to the site by bus. Arrive early for the Visitor Center museums and to stroll the grounds. Plan to stay later for the USS MISSOURI Memorial (a free shuttle to Ford Island, leaving from the VC) or the USS BOWFIN Submarine Museum (next door to the VC). Eat your meal at the lanai of the Submarine Museum. If you're really into military museums then buy a pass that also includes the Pacific Aviation Museum. You could easily spend two full days among those four activities within a few square miles.
If you're looking for souvenirs or omiyage then eschew the International Marketplace and visit the Aloha Stadium Swap Meet on Wednesday, Saturday, or Sunday mornings. It's only one block away from the USS ARIZONA Memorial, so your two-day military museum trek could be extended for a third day of shopping...