Definitely walk around the resort. Food at GCH (Ohana or if you can’t get in, go to Tambu Lounge and order a couple items to try. We like the Ohana Noodles. Even Capt Cooks has variety. Wailulu bar and grill at the tower is really good. Dole Whip is also fun.
If you happen to like espresso martinis, definitely go to Wailulu for one. Warning, they are really good.
For fireworks, the areas we fell in love with are Sunset point (hill near the bungalows, sitting in a swing but I believe only one can see the fireworks, and over by island tower there are hammocks and more).
We like to watch the families watching movies at night near GCH.
Check out the electric water pageant too, which is typically right after the fireworks. It’s been going on for more than 50 years. Not super exciting until you realize it’s been going on for 50+ years. Becomes a tradition for many.
I also suggest getting a tour at Island Tower. Fun to see the difference in rooms. The 1BR was really well done.
Enjoy, there is so much to do at the resort.