Actually, that side of the island (West Maui) is the only place where something IS going on in Maui. Lahaina, which I suppose is what you mean when you say "Downtown Maui." is within 10 minutes of all the Starwood properties, and it's here that you'll find the only nightlife to speak of -- a ton of restaurants, bars, shows (Ulalena, Warren & Annabelle's, Old Lahaina Luau), a movie theatre, and shops. All the Starwood properties offer complimentary shuttles to Lahaina as well as the sister properties.

Just south of Lahaina are public beaches that are ideal if you're learning to surf or paddleboard. Lahaina is also home to one of the three deep-water harbors on the island, so if you want to book a snorkeling trip to Molokini, charter a fishing trip, take a day trip to Lanai, or enjoy a sunset sail, many boats are docked in Lahaina.

There's also a zipline nearby (though I'd recommend the one on Haleakala), horseback riding, and one of the few lifeguard manned beaches on the island (DT Fleming). Within a 10-15 minute drive is Honolua Bay, which is one of the calmest and easiest to enter (from the beach) snorkeling spots. A short drive away is the Nakelele Blowhole, which is worth a visit. Outstanding golf courses (e.g. the Ritz Kapalua) are nearby as well, if that's your thing.

We've stayed in South Maui (Wailea) before, and while it was more upscale, we ended up driving to West Maui most days because Lahaina has so much going on compared to sleepy Wailea. Now we stay in Ka'anapali exclusively.