FYI, check-in at most resorts is 3-4pm. Checkout is 10am (Starwood resorts) to noon, though most will give you day privileges to use the pools the day you check in/out. My point is to not fly to Maui at 10am and expect to check in. You probably won't be able to check in til 3 or 4.
FYI, there are exactly two activities on the Hawaiian islands that I believe are worth the expense and hassle of making a day trip: #1 is the Pearl Harbor attractions. #2 Volcano on Big Island.
While Maui is my favorite island, I don't think there's anything that is such a must see that I'd pay to fly my family there for one night. It offers nothing that is so special that you can't find it to some degree on the other islands, including luaus, hiking, snorkeling, surfing, cold chilling at a fabulous pool. Rather than pay $600+ in airfare, I'd just as soon check into Aulani for one night, or book a private tour or catamaran for just my family, or swim with the dolphins, etc.
However, if you're set on your plan, I'd either head to Hana (3+ hours to get there) and stay at the former Hotel Hana and body surf at the black sand beach nearby, or I'd head to the Fairmont Kea Lani or Grand Wailea and enjoy the heck out of their pool. But, man, that's a lot of time and trouble to swim at a resort pool.