I have been to Oahu many times, and I wanted to point out a few things. One, I don't know of any hotels that offer free parking. It isn't cheap, either. Count on spending $15-$20 per night at most hotels for parking. Two, the best options for "cheaper" hotel rates are "Waikiki Central" or "Marina Area". These hotels aren't right on the beach, but they are "ok" if you aren't expecting luxury. The Doubletree Hotel on Ala Moana Blvd is a common "3 star" pick on Priceline in the Marina Area, and I was able to book some nights here for $75 over the Christmas holiday. Valet parking only, and a 10 minutes or so walk to Waikiki Beach. Three, most of the hotels in Waikiki are older, and the star ratings are typically generous in Hawaii. I have stayed at "3 star" hotels in Oahu that I wouldn't recommend if things like dirty carpets and peeling paint bother you. Public transportation is very good on Oahu, and you can take a bus to pretty much anywhere you want to go. The drawback is all the stops in between where you are leaving from and where you want to go to. Car rentals can be cheap. I always book my car rental on Travelocity or some other site to make sure I have a reservation, and periodically check the travel sites to see if prices have dropped. Then, once it gets close to my departure time, I will go to Priceline and try for an even better deal. Most times I get one. I wait until very close to my departure time to use Priceline because I dont' want to lock in a price too early. The fluctuation in price is amazing over there. I would strongly encourage you to save one day for a drive around the island of Oahu. It is a stunning drive, and can easily be accomplished in less than a day (with plenty of stops along the way). I would also encourage you to save a morning for a hike up Diamond Head crater for a wonderful view. As for going to another island, you can catch 5 a.m. flights to most islands with return flights the same day late in the evening. The flights are probably around $150 round trip right now. Be aware that driving times are very long on the other islands because 2 lane roads are the rule. No 4 lane highways anywhere but on Oahu. You need to pick a particular destination, because you wont' have much time to drive around and explore. The day will be gone before you know it. The good thing is, if you miss your flight back to Oahu there will be another one in 30 minutes or so. Oh, there is no way I would plan on visiting a neighbor island the same day I am leaving to return home. Way too much risk.