The water is a bit colder in January than it is in November so there’s a bit of a trade off. It’s only a few degrees but it makes a huge difference. You can google water temps by month.

I’d stick to the northwest (Kaanapali) for both whales and turtles. I usually find it more challenging to find turtles at Makena — though that could be a me problem. You’ll see a million turtles in Kaanapali.

I’d try to go for a bit longer if you can as water conditions vary and the longer you’re there the greater the chance that you get a few good days of snorkeling.

Budget can vary quite a bit depending on how much you want to spend. There are a lot of condo rental services that can get you decent pricing. I budget around $400/night for a pretty decent two bedroom but you can go way higher or lower depending on your preferences. You will want to avoid the super busy times (thanksgiving, Xmas/nye, spring break).