I like the Wailea Beach dive site...
Just walk about 50' from your resort to the left - it's actually the left end of the beach there. I'm pretty sure the Grand Wailea is the one under "Entrance" here - if not it's the white building to the left.
http://www.shorediving.com/Earth/Hawaii/Maui/Wailea/d000411.jpg
At one time the Grand Wailea had a tank rental shack there - maybe still does. The south point has some interesting u/w rock formations - sort of overhangs. I saw those big cornetfish (like pipefish) there. Also there's a Trigger there found nowhere else on Maui. Never saw one. We did see some big Puffer's just off shore - like 2' long. Guarding babies. The dive ends around 70' or so and by then you're in an active boat channel so watch if you have to surface out there - esp. the Catamarans, you almost never hear them coming. Somebody posted they've seen Manta's there - I never have.
The bays on either side of Wailea Beach are Polo and Ulua Beach - both good dives. Makena Landing and 5 Caves are about 5? mins. drive south. There's also the Kamaole sites but there's going to be a lot of tourists on the beach there. I don't think they're the better dives either. A dive flag is the law and in that area they check. I've seen the ranger at Wailea with binoculars. If you need one the shops rent them. Parking at some of the sites is going to be a problem, lots are smaller and fill up fast. But somebody is always leaving.
Sites 11-19 here are near where you're staying.
Scuba Shore Diving Site Listing for: Maui, Hawaiian Islands
Tank rentals if there's no Grand Wailea operator now are at many of the Maui Dive shop locations. We stay a little to the north of the Grand Wailea and for us their shop is back on the main road and south about two blocks - it's called the Shops at Wailea IIRC. Also you can get tanks at Maui Dreams Dive Co. in downtown Kihei or B&B Scuba nearby. MDDC does escorted shore dives - so does Shaka Divers. Shaka Doug is here on SB.
The boat operators leave from the boat ramp in Kihei - under a 10min. drive north from the GW. They all go to Molokini Crater and depending on conditions - and which trip you're on - they'll either dive the front side or the Backwall. With your dive count, I'd go for the back wall - although there's some good dives off the tips of the crater also. Shark Condos is one...
Ed Robinson's Dive Adventures runs a 3-tank Advanced Charter weekly. That one may get you back mid-later afternoon. If you don't want to be gone that long they also have a 2-tank Advanced. Other equally good options in that area are B&B Scuba or Mike Severn's Diving. Severn's DM's are naturalists so you'll learn more on the ride over/back - takes about 15-20mins. Except for the Advanced, all the morning trips are typically 1 tank at Molokini then hustle back before the trade winds pickup for a 2nd Maui offshore dive. Depending on how the dives go, you can be back as early as 11AM. Notice the check-in times - all around 6AM.
Excellent brunch at the Grand Wailea...