I just went through the "trying to do it on a budget" trip in May. I was going to do one week at Aulani and 4 days in Maui. However, when I started considering the airfare to Maui and the hotel stay in Maui, I decided instead to do 11 days at Aulani on my points and on one of those days take a day trip to the Big Island to do a volcano tour.
I flew from Dulles to LAX and spend 3 nights at GCV. I had not been to
Disneyland before, so I figured this would be a good opportunity, plus it would help break up the trip.
From some of the Hawaii-related expenses that I can remember (to the best of my memory!):
Airfare from Dulles to LAX, LAX to Honolulu, Honolulu to Dulles was about $830. I also upgraded each leg to economy plus, which added another $200 or so to the total cost of the airfare
Standard car for 11 days in Honolulu from Alamo = $212 which included tax. I booked through Alamo and did not use Priceline. I booked early but kept looking for price drops. Best prices started around 3 weeks before I needed the car.)
Aulani tax around $55 (11 nights in a pool side studio)
Gas for car around $60
Day trip to Big Island around $360
Polynesian Culture Center around $150 (booked through Aulani since I wanted to have transportation to and from the PCC)
Snorkeling with Dolphins and Turtles Excusion - it was a special I found on the internet thru Travelzoo for around $69 (regularly $144)
Spa treatment at Aulani - I figured that I was being so "cheap" with everything else that I would splurge on a spa treatment. I think with the service charge it was around $270.
Groceries for 11 days around $70 (shopped for groceries at Target, Costco, and Safeway; I did bring some things from home, like peanut butter and breakfast bars). I ate breakfast in the room every day except for one. I often ate both lunch and dinner there, too. Mostly sandwiches, fruit, carrots, etc.
Eating out - this is where I saved the most money - I had one meal at Aulani which was the character breakfast at $38 including tip, I ate at the Outback one night (around $20), I ate at Sbarro's at the mall one day (around $10), and my cheapest meal was the $1.50 hotdog and drink at Costco. I did buy quite a few shaved ices at Aulani ($3.75 each) as well as ice cream sandwiches (I think around $3 or $4 each). I also got a refillable mug, but I didn't use it as much as I thought I would. I only got one adult beverage around the pool, which was about $10. Be sure to budget for stopping by the Leonard's malasada truck - I probably spent $15 there.

When I went on the excursion to the Big Island, I was responsible for getting my own lunch and dinner - I probably spent about $20 that day.
I did get some things to bring back - mostly macadamia nut type products that I gave to various people. I got all of that Costco for about $72 (6 cans of macadamia nuts, 6 boxes of macadamia and caramel clusters, and 6 boxes of chocolate covered macadamia nuts.) I also bought some more macadamia nut products on the Big Island at the Mauna Loa store - around $25. Can you tell that I REALLY like macadamia nuts?
Other things I did: Pearl Harbor - this was essentially free; Haunama Bay - I got there a little after 6 in the morning and they hadn't started charging for parking or the park entrance fee so that was free; drove around the entire island; went to Punchbowl National Cemetary - free; the only I didn't do that I wanted to do was hike up Diamond Head.
After I got home, I decided to tally up everything to see how cheaply I was able to do the trip - extra expenses included staying at hotel the night before I flew out of Dulles, various tips for tours that I took, some other souvenirs I brought home for my parents, parking at the Honolulu airport the day I flew to the Big Island, my Disneyland 3 day park hopper, transfers from/to LAX to GCV, food at DL since I wasn't able to get to a grocery store, buying food on the plane rides, and I'm sure there is more that I'm forgetting.
I think my "cheap" trip ending up costing me around $3,500!!! However, given how much I did in those 2 weeks and the fact that I stayed in REALLY nice resorts, I thought that this was a pretty good bargain. I priced just the cost of the rooms alone if I had paid cash for them rather than using points, and that would have been at least $8,000!
Have fun planning. I loved Aulani and thought it would just a "once in a lifetime" type trip there. I'm already figuring out how to use my points in the few years so that I can go back there in 3 or 4 years!