They've got scooters at the Westin Kaanapali Villas, as well as tanks. I think they quoted me $100 for a shore scooter dive, but it's guided only. I snorkeled there, but never found the reef, if there is any. If you're considering it, I'd call ahead and ask about tanks, they may only rent 62s, and I don't know whether they require it be guided. They also do SNUBA demos daily in the pool and offer trips from shore, if you're trying to get the wife hooked.
If you're looking for a condo, there are lots in Kihei/Wailea, though it would be hard to beat the likes of the Westin for distracting the wife and baby so you can slip in. Get that line of credit lined up first. There may be similarly situated condo resorts in Wailea, I don't know. As to west vs south, I'd say it's a toss-up, both have some nice spots.