Help needed on Kauai, Big Island, Maui trip

Ok, pretty well figured out our itinerary for our 3 week trip to Hawaii at the end of September. Just wondering if I could get some input regarding beaches, snorkeling, and diving. We'll have 9 days in Kauai (we like hiking), 9 days on the Big Island, and 4 in Maui. Will be traveling with parents and baby

Kauai I'm going to try to get out to Ni'ihau since we'll be getting there Sept 20th, if it's not possible will do Napali Coast dive to Mana Crack with bubbles below. Don't think I'll dive more than the one day on Kauai, too much hiking to do, but would like to snorkel. That time of year what's our best bet for snorkeling, and also generally nice beaches for swimming/walking for my parents?

On the Big Island, will do a combo Manta and Pelagic Magic 2 tank dive with Big Island Divers. And will rent gear and tanks from them for two days to do some shore diving. Seems two step is a must do, where else should we consider going on our 2nd day that time of year?

Would also like to do some snorkeling on the BI, is it worth sorkeling two step if we dive it? Should we go to Captain Cook to snorkel, is it that much better than other sites that don't require a 3 hour return hike? Basically looking for recommendations on beaches for snorkeling, shore diving, and again just all around nice beaches to bring my parents and daughter. Was thinking of staying on the Kohala Coast at a resort like Mauna Lani but debating whether we should stay close to Kona because it makes diving more convenient?

And finally Mauai, I want to dive 2 days, one at Lanai and the other at either Molokini or Molokai. I started a thread last week but still can't figure out if Molokini is actually worth diving or if it's overrated, so many extreme opposite opinions on this dive. And if it's worth diving, if Reef's End is the best spot. My other option is Molokai for the hammerheads but that seems really hit and miss.

Well that's about it, thanks!

Molokini is definitely worth diving IF the swell is up and the inshore viz is blown. Otherwise, I'm convinced I have seen just as much while shore diving (and the second dive from Molokini is often one of our shore diving sites, just the offshore edge of it).

If you go out of Lahaina, the trip over to Lanai, though, is worth it. The Cathedrals are beautiful, and the pinnacles have some dramatic structure.

The night dive on the Carthaginian and the Mala Pier is wonderful (Lahaina Divers).

In addition to the sites on Maui mentioned already. There is a site called Monolith around Lanai- beyond the Cathedral sites that was really good.

You're trip sounds awesome! A couple quick thoughts.

1) You may need to do a pre-Ni'ihau dive depending on the operator. Depending on your cert level /log book / most recent diving they may want to have some time in the water with you before they take you over. For instance they inquired into my experience diving in current. I personally liked the snorkeling and diving at tunnels on the North Shore. Beautiful beach. Depends where you are staying.
2) Big Island, I'd shore dive two-step/city of refuge, and I'd also dive Puako up in Kohala and Kailua Bay (especially for nite diving). I'd still snorkel two step. If you are heading to the other side of the island there is great snorkeling at Wai Opae tide pools in Kapoho. Night snorkels are particularly great. We snorkel there for hours--love it. Also, you can snorkel off beach 69. Its not the best snorkeling but it is the most awesome beach (in Kohala). It has shade. If you want to do two-step (and points south) I'd stay in Kona so you're more central. It just depends on how you feel about driving.
3) Maui. Lanai is a no brainer. Love Cathedrals. We go to Molokini everytime we're in Maui. Of course I'm happy on most dives (I still like turtle town). That said, if you're hunting the bigger/better experience Molokini this might not be for you. On the plus side t's a fun dive (easy) and others in your party can snorkel it. I really like the back side but it can be a bit tricky getting back on the boat. Best bets for shore diving are Makena and Five graves (right next to each other) and Ulua (sp?). Everyone I know whose tried to get to Molokai hasn't been able to (sea was to rough, not enough divers signed up). I recommend booking but having a back-up plan.

Have a great trip!

If you did want to stay north of Kona, both Kohala Divers and Waikoloa Coast Divers keep their boats in the area. Maybe they rent tanks for shore diving also - IDK. If you plan to go to Volcanoes Park it's an extra hour or so from that area also. I'd second the recommendation to stay near Kona - there's much more to do there for non-divers. And more options for dinner etc.

The Poipu Beach(es) - there's about 4 of them - should be nice in Sept. since they're on the south side of Kauai. And shallow and one is breakwater protected for kids. There can be a lot of tourists there. Check with Fathom Five/Ocean Quest since they guide at Tunnels but I'm guessing it might be too rough by then. If you can't get out to Ni'ihau you likely can't dive Tunnels.

My only comment is on the Molokai hammerhead shark dive. The ocean should be fairly calm in September, but it is still very much an advanced dive. It is deep, and there will be current, and there will be hammerheads. Boat exit andre-boarding can be dicey if the ocean is rough, as the boat will not tie up to anything. If your experience and competence level are in fact advanced diver level, you should certainly do the dive, though is costs a bit over $200.00 last time I checked.
Molokini is worth onetime visit, if for no other reason that the visibility will be 150 feet or more, and if it is a sunny day the ocean itself, its cobalt blue with gold flecks, is reason enough to go.
Lanai is a great choice- lots of excellent dives there. Have a great trip.
DIvemasterDennis