I'm reading this thread with interest too, because I'm planning to take my parents on a tour around the islands after a work trip coming up. Will be following a lot of the same advice on restaurants/places to see -- I want them to have a good time without breaking the bank.

I managed to set up some good deals on Priceline so far, and hoping that I don't regret what we get stuck with...:

Oahu two nights, Hyatt Waikiki for $129/night, compact car for $17/night
Island air flight at 5000 UA miles each, to Kauai
Kauai two nights, Resortquest Kauai at Makaiwa for $100/night, compact car for $25/night
Island air flight to Maui
Maui two nights, Royal Lahaina at Kaanapali for $95/night, compact car for $20/night

I'm really hoping the Royal Lahaina works out, because I read that the old part of the hotel is kind of ratty. I would have liked to choose the Hyatt there too, but it's beyond a reasonable price for us I think without Priceline. (during the 2002 travel slump I managed to Priceline a room at the Hyatt for $65/night for 4 nights! what luck, no more.) But I called the Royal Lahaina up to check on the reservation, and the reservation is supposed to get a garden view in the new renovated tower that is reviewed well in the blue guidebooks.
Likewise, in Kauai, I hope the Resortquest doesn't stick us in a shabbier room because of the Priceline thing. The big thing I'm debating is whether to send my parents on the Birds in Paradise ultralight trike ride for an hour, to see the Napali coast and the canyons!

Thanks for the parking garage tip in Waikiki -- that will be a lot better than $25/night parking at the Hyatt!