There should be fireworks over the lagoons, but they are not presented by Disney. The show is funded by the Ko Olina development group that manages the whole area, AFAIK.
I can't answer specific to Aulani or Oahu, but were on the Big Island last year for the 4th and had not anticipated how much earlier the fireworks would be than what we are used to. The sun sets so much earlier that the fireworks were at 8 pm (where we live, they are typically at 9:45-10 pm).
Dreams Unlimited Travel is committed to providing you with the very best vacation planning experience possible. Our Vacation Planners are experts and will share their honest advice to help you have a magical vacation.