Dining you repeat each restaurant 3 times. It was hard to predict what dates would be for special events in dining ie drawing, Mardi Gras, but you should be able to find out on board.
Excursions depends on what you want to do. I did all of my excursions privately and some of them were amazing. The least one we liked was the Road to Hana which is pretty much a one and done deal. It is so long and one of my family members was not happy with too many turns. The road was bumpy in certain areas which I also had a family member which was sensitive to that too which didn't help.
The one we really loved the most was in hilo and doing volcano national park.
Last year I did Hawaii and did excursions through
DCL since there were limited stuff. Now that tour operators are up and running read the reviews. Find things your party wants to do and go from there. DCL does go to volcano national park but it's like a preview. You don't experience lava tube. You just see a crater from a higher up view and get to experience steam vent. I did a private tour and got to see a lava tube, steam vents, see the crater from a different view from DCL and it was amazing seeing the whole picture of it. I saw black sand beach too.
I highly suggest doing private tours because even though it's a little bit more expensive, they are focusing on what your group wants to do. They will spend more time on areas you want to stay in. Try to find 1 thing your family wants to do and then see if they can add on other things or see if it's already included in the tour.