Aloha. I can only speak for us here on Maui.
1st. Don't buy a suit or anything else for that matter in ka'anapali. (A t-shirt in Wailuku is maybe $12, in kahului, it's $15, in lahaina or kihei it's $20 , but in the resorts, your looking at $25 for the same shirt)
Snuba is pretty cool. it's like a scuba tank that floats on the surface with a air hose that goes with you and the mask, so you can snorkel and dive a little deeper and still breathe. thats on the west side of Maui
As for as kids, if he stays in the resort areas, by himself, he'll be safe.the malls and stores or ok too. I have 2 teenage girls,most haoles shouldn't go around some place by themselves anyway. I'm an ex deputy, so they know me. As far as museums on Maui, in wailuku theres the bailey house museum, the baldwin house in lahaina town, and the chinese museum, the wo hing temple, plus the jodo mission has the 2nd largest buddha outside of japan, the whaling museum at the whalers in ka'anapali. you may see a couple of places calling themselves museums, but they are retail store trying to get you in.....BUT there is a lkiller surf board museum in the honolua surf co. surf shop in the lahaina cannery mall. Maui ocean center in Ma'alaea is the best aquarium in the whole us except maybe atlanta. check it out at mauioceancenter.com. aloha, mahalo and good luck. or as they say here malama pono(take care of yourself)feel free to ask anything. bubbamulkey@yahoo.com