I think Maui Dreams Dive Co. has a divebuddy sign-up sheet at the store. At least they used to. And there's a group of local divers who'll probably see your post. Repost an update closer to your arrival when you've made your certification plans, there's always someone willing to take out a new diver if asked.
If you'll need local transportation,
Shaka Doug has the divebus...he's an SB member as is
Blesi Varney of B&B Scuba.
There's also a local Kihei/Wailea area public shuttle. I used them once to go from our condo in Wailea to just past the Kihei Boat ramp - where B&B Scuba, Ed Robinson's and Mike Severns all load for boat trips. I found it in the phonebook.
Definitely dive Molokini Crater during/after your certification. It's one of the best dive sites off Maui. Also there's several really good shore dives in the area: Makena Landing, 5 Caves, Wailea Beach etc. Shorediving.com lists options for all the islands. You could also dive Black Rock at the Sheraton - north past Lahaina - maybe your friends would hang around the resort while you dove. Or if they snorkel, they could do that above you there. It's a fairly shallow easy shoredive. The current will push you in one direction so do it when you've a little more experience.
If you get over to Kauai, Koloa Landing is an easy shoredive and Sheraton Caverns is a great dive just off the south shore (boat dive) with big turtles all over. And it's a fun dive, you swim through exposed lava tubes mixed with short covered areas. We used Seasport Divers in the Poipu Beach area. You might find it more difficult to find a dive buddy on Kauai, there's less diving there than Maui so probably book boat dives if you go there.
Any of the dive operations in this post are generally recommended here on SB.
I'd also consider the Big Island, in addition to good diving, they have Manta Ray night dives and the Volcanoes National Park. But since the volcano is at elevation, you can't drive up until 24hrs. after diving or you risk decompression sickness. After diving a month on Maui, you should be comfortable with a night dive. I've known people who've done them after 20 or so dives.