Disney's new Aulani resort is meant to be a playground for the entire family. In addition to luxuriously appointed rooms, there are pools, water play areas, lazy river, an absolutely beautiful spa, and several restaurants. Aulani's protected lagoon provides a wave-free beach for splashing, swimming and even snorkeling. Childcare is included at Auntie's beach house, a huge facility that accommodates children aged 3 and up.
If you stay for 3 days or fewer, you likely won't leave the property, but Aulani does offer excursions for families or adults at extra cost. Alternatively, you can rent a car for the day on property (which avoids both the airport rental surcharges and parking charges at Aulani) and create your own excursion.