Your family will love it! Haven't been back to Maui since the fire but I know Lahaina Divers is not currently operating. I don't think Lahaina Harbor has reopened to dive charter boats so many if not all operate out of Maalaea, to the south. Shore diving is an option around Lahaina and Kaanapali. Here are some tips I have to help you:
That being said, I think Mala Pier aka Mala Wharf is a fantastic shallow water dive for OW divers (actually all diver), especially if they like Finding Nemo. Not sure how it's accessed now, but it used to be accessible from a boat ramp in Lahaina and from a dive boat. It's 30 ft/10m dive in an aquarium. The collapsed pier is like a wreck with swimthroughs. Tons of diverse sea life: turtles, rays, nurse sharks, trumpet fish, needle fish, parrot fish, octopus, frog fish, etc. etc.. There's a purple wrasse/parrot fish named Christopher that plays with the guides like a puppy. I've seen dolphins there. Good for multiple dives over multiple days.
Humuhumunukunukuapua'a - it's the state fish, the reef trigger. You will see them everywhere. Bonus points learning to pronounce the Hawaiian name.
The inside of Molokini Crater is kind of sad. Decades ago it was fantastic. Now it's a bit dead. It's still a big tourist attraction but compared to it's former glory, it's grey and not as colorful and not a ton of colorful diverse fish. However it is 65 ft/20 m of relatively calm ocean, so would be good for an OW diver. I cannot comment on the backside of Molokini because it's been decades since I dived it.
Cathedrals at Lanai. I love diving in Lanai. IMHO it's the best of Maui diving in and around the lava tubes. It's cavern diving with tropical fish. Bring lights. The Lanai boats used to leave from Lahaina because it was closer. From Maalaea is a longer boat ride. It can be mild chop on the surface, so maybe not a great first dive for new OW diver until they get themselves sorted out. It's also deeper water 65-100 ft/20-30 m. Cathedrals are best done with an experienced guide who knows all the best attractions - like the shotgun exit from 1st Cathedral.
Molokai. Not for inexperienced divers but I throw it in for posterity. I'm not even sure any dive boats go there now because it's so far and crossing the channel can be rough in 6 ft waves. Drift diving in current with the chance to see schooling fish and hammerheads. TBH hammerheads are shy so it's hit or miss seeing any close. Entry and exit can be extra spicy in 4-6 ft swells.
On an off gas day, the pineapple plantation tour is an experience. Educational and fun and tasty. Did you remember the name of the state fish? Could come in handy, just sayin'.
