I’ve only been to AUL for longer trips, but I would say if your family really loves Disney, it’s worth a visit, it just may not be that relaxing. I would try to get there by lunch on check-in day, explore some is the dry activities (lunch, the kids adventure quest with the iPads, maybe send your kids to aunty’s beach house?) then try to do pool slides and beach for a few hours while waiting for your room to be ready… I probably wouldn’t do the Aulani luau if you only have 24 hours but if you aren’t doing it elsewhere you can give it a shot. Have dinner somewhere near by (or at off the hook, or AMA AMA if you are only adults), consider relaxing in the hot tub at night or doing the star watching activity.
In the AM, you could get up early and squeeze in a bit of pool or beach time before checkout (do not expect a late checkout, I think they are nearly impossible?) or try to get the departure day lounge reserved. You can try to do Makahiki brunch late (after checkout) on Day 2, then chill under an umbrella by the ocean or pool—- or perhaps reserve a casabella or cabana for the day to take a home base after you lose your room? Perhaps a spa appointment? Meet characters?
It won’t give you that relaxed Hawaii feeling but frankly, I don’t think Aulani ever feels relaxed to us, even with a 7 day stay…there’s just too much to do.