Don't know where you got the "honeymooners" idea. Every time I go to Maui it's packed with families. Disney even has a huge resort there! I'd try air bnb around the areas of Lahaina, Kaanapali, or Wailea. Stick to the west shore. The sea on the north shore will be very rough, and Hana, though stunning, is a very long drive from anything else.
Thanks, we’ve been to Maui before but the other family hasn’t, they’re keen to go but I’d rather go to a new island and like the sound of Kauai....but friends have had others tell them the beaches aren’t great and there’s not enough for the kids to do, surely that’s not true? Although it sounds like the weather might not be great on Kauai in March?