any advice for traveling to Hawaii?

It may be less of an issue now, but if you are considering a car rental, start looking now, but watch and hope prices drop. There is a national shortage of rental cars sending pricesnthrough the roof. If looking to be there during a peak vacation time, consider an island and activities that don't rewuire you to have a car.

I would like to go to Hawaii in the fall to see my daughter who is in grad school on Oahu. Right now, airfares are pretty good. However, rental cars are about $100/day. Unless you are happy on Waikiki beach with perhaps a few excursions with a tour or on the city bus, I'd chose another island where you do not need a car. Also note that if you have more than one carry on suitcase, the city buses will not transport you. Your options from the airport are taxi and UBER/LYFT. When I was there in March it was a struggle to get UBER or Lyft. I'd look at an island where you can get by without a car.

I would agree to choose an island that doesn’t require a car, eg. Oahu. We chose not to do our yearly 3 week visit to Maui this year. We have always paid less than $700 for a compact car. Now it’s about $2000. Perhaps things will improve by Winter?

I just booked a Hertz "compact" for HNL. Weekly rate for pay at counter is $819 + $200 taxes and fees = $1018. Hotel parking on Oahu is typically extra and in the past valet parking with in/out ran $25-$30 per day. Depending on your vacation objectives, doing without a rental car will be a big savings. If you are on a "lay down" R&R trip, consider taxi/ride share and The Bus alternatives to a rental car.

Be prepared to spend BIG $$$.

Had explored going but our favorite places to stay were either unavailable for when we wanted to go or were TRIPLE the price from 2019 (For non T-Giving Nov.)

If your planning to go between Dec 18 and Jan 3, your in for some sticker shock. I'm looking at that time frame as well, with the grandkids out of school then, everything is very costly. On Oahu we prefer the pristine Ko Olina resort area on the East side over wacky-Waikiki, but there is more shopping and eateries in Waikiki plus it has a zoo and aquarium for the kids (check for hours of operation). There are also the beautiful Kailua and Lanikai beaches on the East side, and the famous North Shore beaches and Haleiwa-town if your looking for beaches. But in the winter the North shore can be dangerous with high surf, which draws crowds to watch the pro's do their thing. I'm expanding my search this go-round to include Maui and Kauai.

I believe the Ko Olina Resort is on the leeward (west) side of Oahu.

Ko Olina and the Disney Resort on are the west side of the island. There is little to nothing close to Ko Olina but if is very pretty over there.

We've booked a package through Southwest to Maui in early December, and the rental car add-on was $350 for 7 days. Are we to expect that there will be additional upcharges or just plain unavailability when we show up? In other words, are the rental car companies meeting their commitments, or is it a general mess?

As noted, Christmas break is high season for accomodations pricing. But a lovely place to say "Mele Kalikimaka!"

When you say Hawaii does this mean the big island? If not then I recommend Kauai and seeing the Napoli Coast. This is the most beautiful island of them all. Once you decide what island to see, buy a Revealed guidebook: https://www.revealedtravelguides.com/.

Get your rental car and be prepared to $$$ for it. I checked Costco and they are sold out for most of the rest of the year but I did find some through my chase credit card.

In December I always pack a rain coat and light jackets.

If this is your first trip .... I think Maui is a great, albeit expensive, choice.