Hmm. I've looked at the points required for a stay at the Grand Wailea, because that's our #1 choice for a staycation ... hands down best pool on Maui, beach has the softest sand, and I think its a stunning property (our other staycations tend to be at the Westin/Sheraton properties though, which are nice, but not as nice as the Grand .... haven't stayed at the Ritz since we don't know anybody who works there to get us a discount).
You're better off, as usual, renting your points and paying cash. At 84-100 points per night, a room usually rents in the $400-600/night range, depending on the season (sometimes you can catch it for $250ish in the very off-season) so you could get 1.5 to 2 nights for the amount of points they'd charge you ...
Can't help much with Kauai since I haven't been there since Iniki, but for all of Hawaii, VRBO is a good way to go, as a PP suggested. Perhaps rent points with one of the professional facilitators and use the cash that way?
Side note:
Btw, Aulani is gorgeous, and its on a more "island-ey" side of the island, farther from Waikiki and civilization just in case that's what dissuades you from Oahu. But to each their own. I don't know if I'd fly across an ocean to go there ...