Hopefully others who have been to Aulani will chime in....
We are going for a short stay in July and do not plan on renting a car. We want to stay exclusively at Aulani and take advantage of all it has to offer. We've been to see the sights of Oahu on a previous visit so no Pearl Harbor, etc. for us this trip. If we change our mind, though, once we are there and want to visit the North Shore, we will rent a car for an afternoon from the Alamo desk on-site. We might lean more heavily toward renting a car for our trip if the cost to park at Aulani was not 35 per night. That is very high and would be hard for me to swallow, especially since we anticipate not using our car each day.
I have read many posts where Aulani guests say they would get tired of staying there for so many days due to the remoteness of the Ko Olina area (not much to do), lack of Aulani restaurants (get bored easily with the few available) and so on, so these guests have recommended renting a car to be able to go out and do things and to eat at restaurants around the island.
Your plan sounds totally relaxing to me, and I would have no problem taking a cab here and there or renting a car from the on-site desk now and again. Look at this way...since you won't be paying 35 to park each night, you'll have some transportion funds already in your pocket to use when you feel like it. Even if you are
DVC owner and wouldn't have to pay the daily parking fee, spending a bit of money a few times for a cab or car would still be a lot less than renting a car for the entire two weeks.
And, finally, if you get to Aulani and think to yourself "what in the world was I thinking by not renting a car?" you could then spring for a rental for your entire stay. I see lots of options open to you.
Good luck with it all. I hope you have a very magical vacation!!