Since you had already booked with Scuba Shack before even asking questions here, I am now really only typing to lurkers who may be planning ahead for their Maui trip.
If one is visiting Maui it is usually at least a 5 day visit. Only the most dive addicted would be diving every day so ~3 dive days is very common. Historically, any list of the most recommended dive trips in the State of Hawaii has always included Molokini and Lanai in the top 5, maybe even the top 3 (with the Kona manta night dive).
Typically, hammerhead sharks at Molokai and monk seals at Niihau are more of a "I've made all the other trips and I have money to burn so now I will pay a lot hoping to see animals most Hawaii divers don't get to see."
If the visitor is staying in South Maui this is a good way to go IMHO;
Rent what you need from Maui Dreams Dive Shop,
for a week. In the OP's case that would be BC, reg and computer; $110. Adding weights for ~24 hours of shore diving is only $3.
If you want to really get the best Maui has to offer, the weather has to cooperate, but the weather does cooperate more than 80% of the time. :blinking:
This would be my ultimate 3 dive day itinerary;
Dive Molokini on Thursday with Mike Severns Diving, letting them know when you book that you are going to do Extended Horizons Thursday afternoon Carthaginian charter and you are going to do 5-Caves as a shore dive. :kiss2:
When you book the Extended Horizons Carthaginian trip, let them know you are diving Molokini with Mike Severns Thursday Morning. Since this is an ultimate itinerary, 3 tanks of Nitrox would make it better for the Carthaginian dive.
Dive Lanai on Saturday with Extended Horizons. Saturday is really just selfishness on my part.
Do a day of shore diving; I know a reasonably priced Sunday guide for Makena Landing/5-Caves/Turtle Town. Weights are included on those Sunday shore dives! See last sentence of previous paragraph.
The Maui Dreams rental computer tracks all your dives, instead of the boat's rental computer only tracking your one trip's dives. Because of the Maui Dreams rental you save $10 off your Mike Severns trip, $30 off each Extended Horizons trip, you get to use the same gear on every dive and you can make shore dives whenever you want.